I'm with many other players on this board.

If I were to find out my friend was cheating in some way, I would tell them my opinion about the matter (and the risk to their account), then leave it alone. Most of my friendships have lasted too long to be ruined over something like disagreeing about the ethics of cheating in online video games. I wouldn't assist in any way, but at the same time I wouldn't go out of my way to report them.

That being said, I would have the biggest, "I told you so" face prepared for them should they ever get caught.