Mr. dB said:
It's a game. Games are fun. Or they're supposed to be. The karma message was a fun way to play tag with your friends, a third line of communication after the form message and PM, and a fun way to gross people out with ugly pictures that can't be posted on the open forum.
It was an additional form of motivation for some people to bother logging onto EF. Way to go, to give people one less reason to come here. Brilliant business move.