Just like Moraff, I write "Ask for Photo ID" on the back of my card. Amazingly, I am hardly ever asked to show it, but it's getting more common that they do.
BTW, I was in an Ontario casino and they had a big sign saying that they would not accept any credit cards that were not signed. This included my card. So now I both sign the card and write ask for photo ID.
If anything, I'd be more willing to shop at a store that take fraud seriously..