One of the few multiplayerish components of the Nemesis System are the vendetta missions. When a friend who also plays Shadow of Mordor is killed, their revenge target enters all their friend's game. If that friend then avenges their compatriot, both players reap the benefits. I just switched over from Xbox Live to PSN (because of the added content for PS4 users) and I don't have many PSN friends.
So if you want more PSN friends add KaDreamer and/or feel free to leave your own PSN gamertag below.