Signing back of card?

[Anonymous]

I have had it happen twice in Vegas over the last few years where a cashier would not take a card because it wasn’t signed so now I sign them all.  As LTL pointed out earlier in the thread both Visa and MasterCard require a signature as part of their credit card agreements.  Putting ‘See my ID’ does not meet that requirement and personally don’t see any reason not to sign the card.  Yes the vast majority of times no one looks or even handles your card but all it takes is one time for a card not to be accepted because it’s not signed to change your approach.

[MoneyBurns]

My thoughts are the same as Irish's, as it says it isn't valid if it isn't signed, and using the card is agreeing to all their Visa and Mastercard legal mumble jumbo. What about the ones that don't say to sign the back? Some cards don't read the, "not valid unless signed" are those subject to needing to be signed?