I have to agree with MelissaAnn. In order for the card to be valid it has to be signed, if you wish to have someone double check your signature, write SEE PHOTO ID next to your signature. Every card in my wallet is signed, then with my trusty sharpie, I have written SEE ID. Most commonly I have been asked to see my ID, and the once I was told to sign my card, I was able to tell the clerk he needed to pay closer attention to the card.
Unfortunatly, it really doesn't matter anymore, I have customers who were sitting at my desk while transactions were going through their card (same card number they are presenting me) on the other side of the country. My opinion, the best thing you can do to prevent this type of fraud is watch your card accounts as often as possible (internet), with a minimum of monthly (statement), to ensure invalid transactions are not being processed. This will help you and your bank minimize any possible loss. The sooner the bank knows, the sooner the card can be stopped.
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The posts I make are those of my opinion or research and not the opinion or advise of my employer.