Facebook. Suggest some friends for your friend.
So I was wasting time on Facebook when I noticed at the bottom of your friend's page there is a link where you can suggest friends for that person. This is a great idea. Now if someone has really awful friends you can let them know by offering them what you think is a better set of friends. I haven't done this yet myself mainly because I'm afraid the system won't be as awesome as I'm imagining it to be. I really just hope that after you pick some better friends for your friend you're able to send them a message telling them why these friends are better. The only exception for the messages though is that you have to be extremely blunt and use less than five words. Honest statements like "doesn't smell", "not a jerk", "not loud and obnoxious", would also help your friend learn what the current friends they have are really like.

