Simple, clean, and user-friendly site. Everything that is needed for you to succeed in the internet. This service looks like it can hit frontpage on DP. Anyways, it looks like a solid and innovated idea. Keep it up!
The first thing that comes to my mind, is that your site appears to promote not so good ways of back-linking and increasing fan following. You should let the visitor know, "How it Works", which will give the user some more confidence in your site to judge if it delivers what it says.