Sorry for the confusion, that was directed at the original poster.
If changing your IP changed your GUID that would eliminate the point of having an ID that is unique to every player. The cost of getting caught cheating would just to be restart your modem and you're unbanned?? Bad idea.
Please don't use the words security and EA in the same paragraph.
In the vast majority of cases I'm sure they're the ones who compromised their CD key. If a cheater has a copy of a serial number there is no way we can just unban the original user without letting the cheater back in.
No idea, but as I understand it someone with a serial number from a keygen is very unlikely to have a "valid" one, and would have to play in a cracked server. If they just happen to land on your serial number with some kind of keygen that is very unlucky because that is not likely to happen.
Fortunately no one would hold that against you if the serial thief raises a PB violation, you just buy a new game and life goes on.