Earlyer on, Glu announced that it would switch from a pure mobile games publisher and developer to one that aims downloadable platforms. Facebook is part of that new target as they released their first game on it.
This new platform also opens up new commecrial possibilities for the publisher as it directly introduced it's own virtual currency called 'G-Coins'. Those G-Coins can be bought for real money and spent in their first Facebook titile. Needless to say, the virtual currency will probably flow into other Facebook games and there might even be a future for it on other (mobile) platforms.