As always, I have a few anecdotes I can share with Betty about this question. As I pondered which to re-live, my friend unknowingly gave me one that is somewhat unique. Although I do have my share of stories about catching a boyfriend cheating on me, and being caught in precarious conversations or situations myself, I decided to go against the typical answer on this one a bit--as a third party observer and ultimately a direct part in a cheating scandal.
Back in the day (about 3 years ago), I had a best friend with whom I had grown very close with in a short amount of time. He was (and still remains to be) one of the best guy friends I have ever had. He has been somewhat unlucky with the ladies (because he always chooses girls who are below him, in my somewhat biased opinion), but he began dating a girl that I actually approved of, in the beginning. She was a friend of mine, and they seemed mutually good for each other, not to mention crazy for each other.
I was happy for him, as a friend should be. Unfortunately, this characteristic of good friendship dissolved as certain events occurred and the lines became blurred between right and wrong. He cheated on this girl with another girl (also a good friend of mine) who he previously dated. This ex of his is manipulative, and not to mention somewhat of an alcoholic, so I can imagine the circumstances under which she seduced him to momentarily abandon his impeccable morals. She told me immediately after.
So the question arose: Where did my loyalty lie? Did I owe it to my best friend to keep his secret, let him work it out like I knew he could? Did I owe it to his girlfriend, my new friend, to inform her, hopefully tactfully, of his indiscretion so they could work it out and she wasn't playing the fool? Did I owe it to my other good friend, who was in retrospect not a good friend at all, who in fact stole multiple boys from myself and others, to expose the boy and destroy a relationship? Should I have gotten involved at all?
Probably not. But we all go through the phase of thriving on drama, and as much as I relished in the sordidness of it all, it turned my stomach to see such blatant disregard of people's feelings. I admit, the events that occurred next do not make me reflect back in pride. I instead continue to be ashamed of my immaturity and deceitfulness, and complete lack of respect and friendship.
But anyway. It was the night of the girlfriend's birthday. For some dumb teenage reason, I was cordially uninvited to the party, most likely because of my association with the "other woman" (who the girlfriend already distrusted, despite being unaware of the tryst). In accordance with dumb teenage behavior, we decided to show up and blow my friend's cover and expose the short affair. We arrived, made a scene, and made some not-so-subtle hints. My guy friend realized what the plan was, and decided to tell his girlfriend what happened before we could throw him under the bus. She left in tears at 1 o'clock in the morning.
Needless to say, my friend refused to speak to me or listen to my pleading apologies. I admit, my morality challenged my friendship loyalty because cheating is wrong in ANY circumstance. We eventually reconciled, and are probably better friends because of it. But catching him "red-handed" and exposing it for our group of friends has had lasting effects, including the termination of two friendships that never really recovered. My guy friend and I re-lived this event the other night, and I confessed to him how I always felt like karma was waiting to pay me back for destroying his relationship. He consoled me by telling me he deserved to be caught red-handed, which is nice to hear regardless of the truth behind it.
Moral of the story? Despite the depravity of cheating, it's best to stay out of other people's business.