Actually, I've found that the CC companies are usually very careful to mail you *notice* of changes - and if you inform them you disagree with the changes, they cut off your line of credit and allow the outstanding balance to be paid off under the old terms. I suspect you also get on a list of folks that have refused changes :)

There was a case a few years back where formula one racers were signing a waiver of liability when they accepted tires from a particular company ... after one died due to tire failure, his heirs successfully sued the company on the grounds that the waiver was improper. As far as I know it's still winding through appeals, and I don't remember the specific arguments. I'd guess that the modification without notification clause is in a similar limbo right now. If that holds up, I'd guess that the valid contract would be the last one both parties agreed to, less that one clause. I don't remember seeing any contracts in the last few years without a severability clause.

If there's no copy of an older contract, I'd think it would be difficult to use it as the basis for anything. Not impossible, just difficult.

I'm not a lawyer, and those are indeed just guesses :)