There aren't many ways to measure the performance of them. The invite module, in particular, Facebook doesn't allow showing stats of. This is because Facebook doesn't want to let admins offer incentives for invites 10 (or 100) people to the site. For the Invites, you can set the "Thank you" link to a special URL that you can track, but that's outside the scope of JFBConnect, unfortunately.
The recommendations are the same. The recommendations are based off of what users Like on your site, so you can help influence that by placing Like buttons on the right pages. I don't believe there's a way to see which links users are visiting through the recommendation module though.
I know this isn't super helpful, but hopefully explains what can (and can't) be done.
Good luck!
how to measure performance of some of the modules
