Puzzle Pirates (www.puzzlepirates.com) has used virtual currency in exactly these ways (for gambling in virtual poker and other games, and buying virtual items

Puzzle Pirates (www.puzzlepirates.com) has used virtual currency in exactly these ways (for gambling in virtual poker and other games, and buying virtual items that can be exchanged between users) since before Zynga was founded. Seems like clear prior art. The one claim that isn't in PP is the limit on the number of times an item can change hands. It's hard to see how zynga wouldn't know about this.