Ghost Friends are friends (both mutual and non-mutual) that take up 1 count of your total friends limit, but don't appear on any friends list so you can't remove them.

Explanation Edit

The reason this happens, is that the friend in question has been deleted from StumbleUpon, but not from your friends list.

Symptoms Edit

The classic sign if you have one or more ghost friends, is that the friends count is different from reality. For example, if you have 195 friends it may say you have 200, stopping you from adding more friends!