I accidently knocked one of my sites from the #1 position for an exact domain search with another one of my sites using facebook links. site A has 3 x PR4 2 x PR3 3 x PR2 24 x PR1 and 104 PR0 all about 80% d0f0ll0w site B (actual linked page) has no other links except the facebook links site a used to be #1 for searches for it's domain name and business name. This site has 1400 genuine Fb friends who receive 2 posts per week. To try to get some extra linkjuice flowing I started publishing the main page of site A to an internal page on my money site (site B) and then adding that link to the FB post. After 3 posts (4200 links) site B is now outranking site A with the same content. Thought this may help someone somehow.