Interesting list of candidates. There are many arguments for any of these. That said, my guess would be with a "portal" whereby ZNGA would drive more online viewers. The portal would derive higher revenues from gambling, pay-for-play downloads and advertising due to increased traffic and premium positioning. Therefore I would list portals in desperate need of a shot in the arm such as YAHOO and AOL in addition to GOOGLE. Facebook and Amazon could easily fit into this profile as well.
No question in my mind.
The dark horse in this has been Apple, and I expect AAPL to make their move very shortly now that ZNGA has been thrust into the news wholeheartedly.