A Huge Moral Question

So there is this guy that I was working with last week and I know he is cheating on his wife and I don't know what to do. I barely know him, I don't know his wife, and I met his girlfriend very briefly once. He is friends with Lucifer, the cheating bastard that I dated (obviously his name isn't actually Lucifer but he earned the nickname quite well) so I can see his myspace page, which links to this guy's, which links to his wife's. His wife's page has this quote on there that just makes me cringe in agony: "Never allow someone to be your priority while allowing yourself to be their option!"

This situation totally sucks, mostly because they have children. Apparently she busted him for cheating in the winter or spring but they are all good now. Or so she thinks. This guy is totally off his rocker. He was telling me that I should write Lucifer a letter so he could take it to him in jail because I was saying that I don't wish him ill, I just want him to get better. (And yes, in a roundabout way I put him in jail...roundabout way, though, I mean he really did this to himself, I just exposed him for who he really was).

So anyways, now I am sitting on this information and I don't know what to do. I know for a fact that going to someone without hard evidence about an affair is really unproductive and destructive. I know when I was cheated on, it was his close friends that had children and families who didn't tell me with whom I was really upset. Although, if one of his random myspace friends had told me that I probably would have given their claims some thought because there were things to be suspicious about. Anyways, I really feel like it's not my place to say something, but I worry I'm just saying that so that I don't have to deal with it, so that I can turn a blind eye and I'd like to think I at least have *some* moral courage. I could use some thoughts on this one. I feel like ultimately I'm powerless in my situation and all that can come of this is discrediting myself, the good Sumaritan.