When guys log onto Facebook, a relationship expert with cosmopolitan says that they are sometimes doing all of the wrong things.Dr. Seth, the relationship expert, says that when guys start to obesses over wall posts, friending, and tagging photos, it may be time to remove yourself from the social netowrk. He goes on to say that the biggest mistake most guys make on facebook is when they hack into their partner's account. At that point, guys have made the biggest mistake of them all.