StingingVelvet: It's generally a good idea to keep old credit cards in a safe place in case you ever need the info again, but yes I agree it can be difficult. I'm sure Valve sees that as our problem, not theirs.
Virama: Actually, with old credit cards the banks tell you to destroy them ASAP. So I doubt this is viable.
Very true - I had to cut up my card (through the chip) and mail it back actually.
Valve are just assholes really - I had the same thing happening to me a few years back and they wanted a copy of the receipt of Half Life. This was in 2005!!! You think I keep 7 year old receipts because some anal company wants to be greedy?
So after several messages with Steam support, they said okay, give me a picture of the CD key tied to your account. So I replied, fine, but I have 5 different ones (I bought quite a few copies of HL back before Steam made them useless - mostly to give to friends online so they could play Counter Strike with me). So I didn't know which one I had used on Steam because, at the time, Steam was freaky and ATE several keys!
So I sent a picture of the 5 cd keys I had, with the explanation and nearly lost my account because they thought I was scamming them or something. Idiots. I had to tell them it was for a local LAN before they finally helped me.