At the grocery store yesterday, I paid with my American Express card. The cashier asked to see my card, and then she looked at the back to make sure that I had signed it. After I signed the receipt, she put it in the drawer without looking at it.
Why did she look at my card?
If my card was stolen and I had signed it then it would be necessary to compare the signature on the back of the card to the one on the receipt to see if they match. If I had not signed the back of my card than the person who stole it would have signed it himself, in which case the signatures would have matched so it would have been necessary to check my I.D. To make sure that I was in fact the person whose name was on the card. However, neither of these two things happened. In fact, they never happen.
I can't tell you how many times I give a credit card to a person in a store and they look at the back and never look at the receipt to see if my signature matches. The whole point of signing your credit card is so that if it's stolen the person who steals it will not be able to match the signature on the card. I don't care if you're not going to check the signatures to see if they match but please don't be so stupid as to ask to see my card and then not at least verify the signature.
Seriously, how stupid to they think a credit card theif is? "Hmmmm, let's see, this card belongs to Mr. Perry and the signature on the back is... Bob Smith! Oh my god, you're not Mr. Perry! This card is stolen!"
It bugs me every time.