I search somebody, who is able to write a plugin for osclass. It is a classified system.
With the plugin you should be able to login in with a facebook account, and then the visitor should see how many mutual friends they have with the advertiser and how many friends of friends they have together.
There is a simpel facebook connect plugin for osclass which only allows to login with facebook but nothing more. You can use this to build the additional features which I've explained.
4 freelancers are bidding on average €182 for this job