Not sure if you've spotted this relatively new American Express 'Social Currency' ad, but Zynga's game CityVille managed to score a starring role. About halfway through, you see someone sharing "I'm Level 5 in CityVille."
Why is a game like CityVille part of this Amex ad? Aside from the its obscene popularity (it currently boasts 88 million players worldwide), you can renew your Amex Reward Points for virtual currency that can be used in Zynga games or to buy exclusive virtual items for FarmVille, CityVille, et al. For more information on which items you can buy, head to socialcurrency.com.