I agree that we all know it is part of the risk "airing" out our problems and many people can relate to it or they can just be morified in seeing this type of thing online. Kids are smart nowadays and sometimes it can be educational in seeing how mature and how adult we can be sharing problem...
It IS cheating, emotionally and physically if he is doing it online. Its the temptation he is going after.
Marriage counseling would be very necessary if BOTH wants it to work!