If this is a fluke, why would anyone expect the developers to be able to replicate the success on other games in the future? I think I read somewhere the current run-rate revenue of draw is around 100k a day. But you would expect that to tail off when it reaches saturation. Probably most of that comes from the initial purchase, rather than in game purchases. So you're looking at more than 6x of current revenue which will decrease over time, just to break even on the purchase, and not counting expenses.
Don't get me wrong, I'm sure the developers are talented, and they deserve getting paid. The only people losing are the shareholders of Zynga, and less the management, since they've been dumping the stock. I think Zynga is probably under a lot of pressure to diversify it's revenue away from Facebook, as well as grow the revenue to justify it's valuation.
Comparing acq of OMGPOP to Youtube is just silly.