barring requiring a credit card number to join an archive/site/whatever

Very bad idea, since in most of the world (except the US) the majority of people don't even use credit cards! That is, here in Europe they don't - only businessmen usually have them.

That's one of those things that keeps annoying me - I can hardly buy anything online because everything's based on the credit card system, which is normal for Americans, but weird and uncomfortable for us here.