"Play Draw Something now and earn Farmville points!"

Zynga points. You can use them across Zynga games to get e.g. exclusive pumpkins in Frontierville. There's a cap which resets every day, so you know when you can stop playing.

What.

[edit to add: Not currently playing any Zynga games. League of Legends pushes my buttons much better.]

As one of my close friends said recently, "yet another Facebook token that Zynga will soon own."