In New Facebook Graph API 2.0 ,Friend list is no longer part of the default permission set and has its own permission: Asking for access to a person's friend list is now a separate permission that your app must request. The new permission is called user_friends. you must change this in our sample on line number 170 FBLeaderBoard.cs
Friend list now only returns friends who also use your app
Sorry.. our sample is also outdated and we will fix this as soon as possible.
Steps for getting friends score from Facebook:
1. Login to Facebook.
2. Link user facebook account using socialService.LinkUserFacebookAccount
3. Get friends score from Facebook using scoreBoardService.GetTopNRankersFromFacebook.