text: The problem with debating whether or not it's justified to confront someone about information you obtained sneakily is that it's a moot point. Once you find out the information, you can't just sit on it. It's impossible. So when you confront, you have several options. 1) You can just plow through the truth, as DeVore suggested, and admit what you've done, 2) You can go with the old "I just have a women's intuition hunch that you're seeing someone long distance" and never reveal your sources, or 3) Figure out some legit way to "discover" the information, preferably in front of him.
  …I once, after finding out a boyfriend was cheating on me, figured out from the girl's MySpace profile what her interests were so that I could show that I was also interested in those things, enough to make her friend me. And once she did, I "casually" mentioned my boyfriend, and BOOM! The guy and I were through, but the girl and I remained weird friends. (Note: I am not proud of this behavior.)
  But I digress. Situations like this remind me of those couples on the Maury show, where the woman feels compelled to drag the man all the way to whatever smelly cave Maury is filmed in to get irrefutable proof of whether or not he's cheating. If you have to resort to snooping or Maurying, rather than relying on good old-fashioned trust, your relationship already needs some work.