[pilom]

This is the biggest downside in my opinion. Theoretically any merchant should deny any card without a signature, End of Story. In the merchant agreement they sign with Visa and MasterCard, they agree that any fraudulent charges where they did not check the signature are their responsibility.

[halisaurus]

How often are the cashiers checking the back of the card? Many of the card readers I see are on the customers' side of the counter, and I swipe it myself, often because I'll enter a pin. Also there are self-checkout kiosks with little or no supervision. I don't think that the lack of a signature line is the _biggest_ downside.