Well I'm the kind of cat who is killed by curiosity. No matter whose email address and password I got, I'd go looking. And not for anything incriminating, dirty, infidelity, etc., just because I'm intensely curious about the mundane day-to-day details about people that goes on.. a kind of "vicarious living" if you will. I'd read their spam and their letters to grandma, and skip the dirty letters to the ex.
If I were specifically wondering about infidelity, I wouldn't go snooping in an email inbox to find out.
I'm the kind of person "life casting" (
http://en.wikipedia.org/wiki/Lifecasting_(video_stream) is aimed at .. not so I can catch anything dirty, but so I can watch Random Joe walk around town, order Starbucks, tie his shoes... etc., etc.