After some tests, it seems the return value for Following after a call to get favorites of a user is pretty bugged.
For example in the same set of results where 2 distincts favorited statuses are from the same user, the "following" field can be different ! (one time false, one time true). The only way to be sure the authentified user who does the favorites query is following or not the writer of the favorited tweet would be to use another api call and compare id with those returned by the friends/id method ? That would be boring :(
