I'm currently in the planning stages for an Web and iPhone game. I'm developing it with Adobe AS3/Air. I was wondering if it's possible for people to be able to play the Web version, save their state of play and then pickup again where they left of on the iPhone version? (and visa versa) how that would be achieved? the Web version will probably be on Facebook, so could I link both versions through their FB UID?
To share persistent state between clients (that could be multiple players, or just multiple platforms for a single player) you need data being stored on a server. Since you will need to host your game on a server anyway for a Facebook app, presumably you can also create a database of player states on that server.