Red letter day on the DIS, four pages of responses and 100% agreement!
Ok, now let's play....let me be clear that I was shocked by the original question. BUT some of the responses did get me thinking...several posters have alluded to the fact that the boss' husband was engaged in a legal activity so of course no need to bring it up to anyone.
However, what if the OP witnessed, say, the husband engaged in a make-out session with another woman? (in
Walmart parking lot, yee ha!

) That's also a legal activity. Would anyone feel inclined to bring that to the wife's attention (pretend it's a friend and not her boss)? It can also carry potential health risks (std's?), shouldn't the friend be aware?
I'm inclined to stick with the MYOB, but I know others will feel differently and think the wife has a right to know if her husband is fooling around! Does that alter anyone's original stance?