Consequences mainly - as you end up with 1 side being dominant too much. With 3 realms fighting, its much harder for any single realm to be supreme. Unless they allow people to roll chars on all realms on the same server (PS did this - but in the early days it didnt matter/DAoC didnt and still doesnt) then it can all go wrong when the victory hounds start changing to the realm that looks like it will be the daddy that week.