Zynga has apparently removed its massively popular game Farmville from Microsoft’s MSN Games, and nobody seems to know why. The timing of this is interesting as Google has reportedly been in investment talks with Zynga, while it has been acquiring other social game-related properties.

While Zynga has offered no comment on Farmville’s absence from MSN, Chris Morrison at InsideSocialGames.com (via VentureBeat) writes:

The departure from MSN looks much more notable, in the grand scheme. MSN itself claims to have about half a billion monthly users worldwide between Games and Messenger — equal to what Facebook claims for itself.

One of the big stories in social gaming right now is that developers are interested in moving beyond Facebook, keeping a line back to the social network’s graph with Connect. With partnerships like FarmVille on MSN, Zynga has been a leader in that move.

The move seems pretty odd to say the least, and I suspect the picture will become clearer before long.

Zynga has been expanding its reach and making moves that should help it expand more in the future. Besides a reported investment from Google, the company recently acquired Japanese gaming company Unoh, and launched Farmville in app form for the iphone.