They never told me exactly. My guess was that I happened to use 3 different CCs, all in my name, to buy the 3 or 4 games I bought over my first few days having the account. I meant to say in my original comment that they did refund everything, so it wasn't as horrible as it could have been but I did miss out on the sale prices, a few weeks of not being able to play a game with my friends, and it left me with an ever-lasting bad taste for Steam and DRM in any form (which is good in the long run I suppose).

We have bought every game with a different e-card an no problems so far. This means at least 500 different cards. E-cards was a service where you could create a credit card with a fixed amount of money on for each buy, limiting the risk involved in giving out your card details on the net. Sadly they shut it down recently.