For me LotRO is interacting with friends. After soloing for a long time, I joined a kin where I met some wonderful people. The first friendships were made. With the friendships, my friendslist grew. And Turbine is so nice as to tell us when friends on that list come online.
However, when you are busy, the message they get online is easy to miss. And how often it happened that I was waiting for a friend and missed the announcement… well, way too often!
Very simple, great pleasure!