Not that anyone should take my opinion as any kind of guide for right action or anything.
     What I'm discussing here are those plastic cards, a little bigger than standard business cards, that we use to pay for things these days. They divide into three categories: charge cards, debit cards, and "other."  What are the pros and cons of collecting any or all of these?

DESCRIPTION OF THE FIELD
 1. Charge Cards have been in use since the '50s.  They started out as in-store customer account cards, then gas stations jumped on the wagon, followed by credit companies like American Express.  Banks got into the act, first serving as agents for the big credit companies (eg Visa-Mastercharge), and later with their own proprietary cards used as local identification to guarantee checks and, since computerization, to do business at automated Teller Machines (ATM).
     Since world finance has become computerized charge cards are everywhere and you can do anything with them.  Probably every bank in the world is hooked up with one or another of the credit companies (Cuban and North Korean banks are possible exceptions), and theoretically issues it's own cards.  So you're looking at multi-thousands of issuing agencies.  And of course most of the cards are valid for a year only, and are reissued annually.  That's a lot of cards to collect.
     And now artwork and advertising is starting to appear on the cards.
 2. Debit cards are the opposite of charge cards.  Instead of advancing you credit or electronically accessing your account a debit card of a given value is purchased, after which it can be used to pay for whatever services it's meant for.  Usually the service is phone calls, but similar objects are used to buy transportation in several countries, and there are other uses being planned or in operation here and there.  Somewhere, I think it's Denmark, there's an experiment in "cash" cards, which you can use to purchase anything.  For collecting purposes debit cards come in two varieties: unused and used.  Worldwide, most cards are meant to be discarded after use, so can then be kept by collectors.  (This isn't exactly true.  More and more are being issued for the express purpose of selling to collectors.  Yes, I have an opinion.  Later.)  There are, however, some hybrid "rechargeable" cards.  When they're empty you use your credit card to fill them up again.
 3. "Other"  Most of these are identification cards - well, everyone knows what they are.  In recent years they start coming out shaped like credit cards, and some people collect them.  Examples include club memberships, schools, health plans, insurance schemes, etc.

THE MECHANICS OF COLLECTING
     The basic problems confronted by collectors of anything are: how do you get them and how do you store/display them.  The existence of reference catalogs may be a concern to some.  Finance is another matter: how much money you will spend and whether you are likely ever to get your money back, let alone make a profit.  I think I'll discuss storage first, because it's pretty cut and dried.
     Many cards will fit in plastic business card pockets, so business card display albums will do just fine most of the time.  A few series are just a little bit too large.  They will fit in baseball card holders with room to spare.  The narrow end is usually 2 inches, which means they will fit sideways in a standard 2x2 coin box, but of course they then will stick out 1.5 inches.  That's how I store them.  Works fine.
Lindner, the German manufacturer of fancy display albums, etc., has some albums designed especially for phone cards.  So, storage can be arranged.
     Catalogs, on the other hand, are a problem.  I've seen a few starting to take shape, but none claim to be comprehensive.  There are books on German phone cards, ATM cards of Hong Kong, Macau, and Singapore, and some USA items.  Most of the books are expensive and become outdated immediately upon issue.  Also, the enormous proliferation of types makes an eventual comprehensive catalog a difficult, and therefore less likely proposition.
     Now how to get them.  Bank and credit card collectors are not well organized, the market, such as it is, is small, and the cards tend to be hard to come by.  After all, they have people's personal account numbers and signatures on them, and possession by someone else of last year's card of a still active account can cause trouble for the account holder.  Many people, wisely perhaps, throw out their old cards when they get their new ones, or if they are willing to let them go to collectors, cross out their signatures.  Occasionally they will mutilate their cards.  They don't really need to do this.  Drawing a magnet across the record strip will kill the card so it can't be scanned.  But try telling them that the next time you go up to someone and ask if you can have their card for your collection.
     And you usually can't go to the bank or write to the company and get a collector card marked SAMPLE or suchlike.  No, bank and credit cards are not available to collectors in sufficient quantity to build up wholesale inventories, so very few dealers can have many on hand at any time.  You'll have to dig for them, and use more ingenuity than money.  Notwithstanding, I know of several people who have put together collections of several thousand types, and a few of these have been purchased by banks and such for largish sums to use in displays.
     For identity cards it's pretty much the same story, though there are no serious potential financial penalties awaiting the original owner should the cards fall into the wrong hands.  There may be some collector clubs, but they are small.  There is no wholesale, therefore no real market.
     That leaves phone (and other debit) cards.  Several years ago collection of these seemed to be booming in several countries, notably UK, Japan, Korea, Hong Kong, Singapore, Belgium, Greece, and others.  Phone card collecting was so popular in Germany that there were hardly any German cards available outside that country for collectors.
     So popular had they become that there were a good number of dealers throughout the world.  There were wholesale supplies, and collector clubs, and you could find ads for phone cards in coin and stamp publications.
    Seems that since I wrote this in 1999 or so there has been a steep decline in interest in phone card collecting, especially on the dealer side.  No money to be made.  In 2003 pretty dead.
     Phone cards have not taken off and become popular collectibles in the USA.  "Everyone" said they would, but it never happened.
     Phone cards come in two flavors: new and used, and collectors tend to sort themselves into those who will not pay the high price of new cards and those who will not touch used cards.  Dealers of course will want to sell new cards, because there's more money involved and they can easily get the cards wholesale through official channels.  To get used cards you have to scrabble around transit depots, pay street urchins and cleanup crews to scavenge them for you, beg your friends, etc.  Enough people do that throughout the world for some dealers to be able to offer wholesale used phonecard lots of 1000 or more.  But there's not a lot of money in used cards for the dealers, so not very many get into them.
    Now in some countries the government issues the cards, has no sense of humor, and won't make private deals.  The cards are simple, boring, and there are only a few of them.  Example: Bolivia.  Many countries started their phone card careers that way.  But after not too long they all seem to figure out that they can sell more cards if they have more designs, and there is a steady proliferation of types in each country.
    Many countries have crossed the line into private enterprise, and take advertising.  And, to bring the situation to the individual level, some countries are starting to emulate Japan, where you can go to the phone company and have cards made to celebrate your wedding, or retirement, or the birth of your daughter, etc.
     The accessing of private enterprise has produced a bunch of issues designed primarily for sale to collectors.  These range from cards commemorating ephemeral events like the Olympics, political conventions, trade shows, etc., to human interest theme cards: ethnics, pretty girls, pop stars, cars, nature (cats and horses are popular in Japan), and so forth.  Some of these cards are offered at fantastic prices, like a set of 4 cards for the 1992 USA Republican convention.  I saw it priced at $1000.00!  I wonder if anyone bought it?  I'll be honest.  I don't understand the unused side of the phone card market.  I mean I understand it from the dealer's side.  But I don't understand the collector angle.  Many of these cards have a high base price, the cost from the producer.  $20.00 is not unusual, and they go as high as $100.00.  This is the price at the source.  The dealers of course will buy in quantity, so will get some discount.  But what collector is going to shell out $20.00 each for hundreds of cards to make a collection?  Financial limitations will usually make collectors of unused cards specialize upon some theme: sports, for instance.  In the 90s there were a number of dealers, individuals and firms, who were maintaining large inventories of expensive unused topical phone cards.  Most are out of business.
     The used card market is more laid back.  Average retail price per card is on the order of $1.00 to $2.00, though a few will go much higher.  A lot of used card collectors are interested in trading theirs for yours.  You will not find the top-of-the-line collector cards in used condition, but there are still thousands of types to collect.
     These cards have a lot to recommend them to collectors.  They are pretty, colorful, durable, and there is lots of variety.  I am worried about the last.  Phone cards have been around for less than 10 years, and already there are tens of thousands of types.  The practices of the Japanese issuer, NTT, make it essentially impossible to build a comprehensive collection.  There are probably more than 10,000 Japanese types, and thousands more are created every year.  It is daunting, and makes collectors feel bad.  If it is not possible to complete a collection, and you can't even find out the true scope of your collecting interest, you might begin to get a bit jaundiced about the things.  It becomes something like collecting display ads or brand name labels.
     And I think that the proliferation of cards whose primary purpose is to be collected is very problematic.  There get to be more and more of them, and the more there are, the greater the level of collector fatigue.  The fatigue builds, and eventually the market gets oversold and goes flat.  That's happened with coins and stamps and baseball cards, and it's happening with phone cards too.
     I am sanguine about the future health of the hobby.  I do not recommend one attempt to collect phone cards as an investment.  That $1000.00 Republican Convention set, does that sound like something whose value is sure to grow with the passage of time?  Because I think people should collect for fun first I find myself touting used cards almost exclusively (in 1998, now I don't sell them at all).  I think that a real challenge, and one worth pursuing, would be to get one card from each issuing country, used.  Topical
themes will also give pleasure.  But don't even think about trying to "get them all."  Can't be done.