The social gaming world is abuzz tonight with word that hot game company Zynga has apparently pulled its hit FarmVille from Microsoft's MSN Games portal. Inside Social Games, which first reported the news, floats a theory about the Microsoft platform possibly not producing enough traffic to keep Zynga interested, but given the volume of users MSN pulls in on a regular basis, that seems a bit of a stretch.

Maybe this is just as much of a stretch, but Google reportedly made a major investment in Zynga recently, possibly setting the stage for the search giant's own video-game site. Coincidence?

At any rate, we have messages in to both Microsoft and Zynga, hoping to find out what's actually happening.

For whatever it's worth, searching for FarmVille from inside the MSN Games portal doesn't return any results. Coming in via search engine, the FarmVille page on MSN redirects to a url that ends in "farmvilleoutage" and a page that says the game "is not currently available."

Microsoft and Zynga announced their partnership in February, with users able to log into the game on MSN using the Facebook Connect identity system. Yahoo and Zynga announced a partnership of their own in May, although the Zynga games don't appear to have rolled out yet on the Yahoo portal. GameZebo raises questions about the fate of that arrangement, given the disappearance of FarmVille from MSN.