Like Mischa Barton's attempts at staying relevant - it doesn't work!
Plus, it's just a real douchey thing to do. You're forcing your friend to give up someone who makes her happy (even if he is a problem boy) just so you can feel better. Most times the guy probably is bad for her, or is just a jerk, but the most you can do (if you want to keep your friend, that is) is voice a bit of concern in the way a friend should. It's her decision to stick with the guy or not, not yours. If it bugs you that much, just don't hang with her when she's with him.
Just something that seems to keep happening like people think it's a good idea from the start.
Also, hi! Yes, I'm posting. How do you do?