Have you ever judged a friend's financial savvy based on the rewards yield of the cards in their wallet? Now you won't have a choice. For those of you that abhor free flights, detest comped hotel rooms and net severe displeasure from earning cash back, AMEX may finally have your plastic match. It's called the Zynga Serve Rewards card -- yes, the same Zynga that's behind time-sink cash cows like FarmVille, CityVille and CastleVille (?!) -- and it enables you to accrue "Zynga Farm Cash," which as you might imagine provides no financial gratification
