We already know that the very popular Angry Birds is coming to Facebook. Some more details are now beginning to trickle down, while the Facebook game will be much of the same Angry Birds that everyone knows and loves, it will have some peculiarities.
There will be some collaboration, as expected, probably something like what FarmVille and company have done, asynchronous 'multiplayer.' But there will also be a leaderboard for some good old fashioned competition with friends with equal amounts of free time.
The game will be free, no big surprise there, but Rovio does plan to make money from Facebook's 800 million or so users, via the old game-maker's friends, micro transactions.
In this case, users will be able to buy power-ups and most likely the Mighty Eagle as well, if they're stuck on a particularly difficult level. The price for any of these goodies is probably going to be $0.99, €0.75 though you'll be paying via Facebook Credits of course.