Somewhat related: a friend and I built a game a lot like this as a Facebook app back in 2009 called Pictionnected. It had a few really passionate users. Didn't really iterate on it, got busy with work, and didn't maintain it when Facebook made some platform changes--eventually killing the app.
I deeply regret not sticking with it. I didn't know at the time just how unique it was to have that core set of extremely passionate users. The thing I've been realizing more and more these days is that persistence really is the name of the game.
In any case, it's great to see that the idea is still alive and kicking!
(Screenshot, for posterity: http://i.imgur.com/pSLNA.jpg)