Just found similar results for my app (Smarter Than My Friends). Profile Add boxes and Product Directory drove 80%+ of installs.
Given that the Directory is such a key driver of current app installs, I'd love to see a comparative study to see if apps that have matching appname and URL (on apps.facebook.com) have higher install rates than other apps. This would run totally counter to some of the "conventional wisdom" I've heard (e.g., "Your app name and URL doesn't matter" -- if the Directory is important, then it could be ALL about naming.
And to push that one step further... Has an economy formed around "domaining" for FB app names?
