In today's ourWorld update, we added a "heart" feature. Each player gets exactly one heart that they can give to a single bestest friend.
Now, it seems, each person will have to pick a favorite other person (or not), declared for all ourWorld to see. Time will tell will see how dramatically this changes the social scene.
Already I can see girls becoming each other's BFF's to avoid choosing a single guy. Not sure that will work for guys who, due to their relative scarcity and the number of available girls, are more frequent offenders.
Note: If you are an ourWorld player who just found out you weren't your sweety's favorite, that cheatin' other person didn't deserve you.