You go to the other side of the city for a dinner date with your wife, when you encounter your best friends spouse out for dinner with a younger more attractive man. The way that they are acting indicates that they are more than friends. So the question stands, what do you do?
Do you, tell your friend, or leave it alone because it is none of your business.
Some cons to the first option could be that your friend may not believe you which in turn could ruin your friendship, plus it would ruin his marriage which could have many outcomes on their kids (IF they have them) and it may have impacts on their financial lives in the future. But if you leave it alone then your friend will never know that his wife is "cheating" on him, which could make more problems when he eventually finds out.
'I should tell my friend that his wife is cheating on him, as it is the morally right thing to do. I can save him a lot of pain and heartbreak in the future if i tell him now'
You pull out your phone and call your friend, telling him that his wife is cheating.
"Hello Johnny, I wanted to inform you that I have seen your wife being romantic and going out to dinner with another man. This may be hard to comprehend and may be overwhelming, but I think you may have to get a divorce"
"I am very glad that I told my friend as it will protect him from any further problems or hurt. Plus his wife can be with the man that she wants to be with. In my eyes this was the right thing to do instead of letting this cheating go on for potentially a long long time'