I don't know what exactly you can do with the API, but I think a pretty good system to make your game popular would be betting on the competitive aspect.
I noticed earlier that MochiAds implemented that feature in their Highscore API. You can log into FACEBOOK and compare your highscores to those of your friends.
I integrated MochiAds and Mochi's leadboard API in my first Flash game recently and it was VERY easy. Also, the Facebook leaderboard tie-in has been great. With no extra work it allows people to add a "mochi-leaderboard" facebook app to their account and it will totally let you do the viral facebook thing where you can create 'challenges' and see all your other facebook friends in the leaderboards. You can invite them to play and when they play, their profile page lists how well they did with a link invite others to play your game as well. They of course get to opt-in and control how much to tell facebook about playing or not.
Pretty good experience with it so far.
Developer
