This problem happens because of the Facebook SDK for iOS.
Application Loader forbids the use of the variable “id” from any FBGraphUser related class (maybe others variables too, didn’t test) – e.g. :
id<FBGraphUser> friend
id<FBGraphUserExtraFields>user
Facebook is informed about this problem as of january 2013 : Bug Report
The workaround for the moment is to use these:
[user objectForKey:@"id"]
[friend objectForKey:@"id"]
instead of user.id and friend.id as shown in the different Facebook samples.