I don't think Amex is the only company that does this. Every once in a while, all of my cards, for no particular reason, come up bust.

Amex, however, has given me the third degree more than Visa when this happens. Amex once threatened to cancel my card if I didn't answer their many personal questions - for a $50 meal!

Visa once told me that I was singled out because I had bought wine (didn't take Amex) and then bought sporting goods (didn't take Amex) later that day. They said that was something a thief would do!

The only thing that brings some humor to these situations is that they always say "this is for your protection." Since I never have to pay any fruadulent charges, these proceedures are clearly for the company's protection, not mine.