I did a little test, I use the term lightly because I didn't know I was going to do it at the time.
I went online into a chat room.  Used my real picture and all my information was correct.  Men started pm'ing me like crazy (no I'm not some beauty queen by any stretch of the imagination), I think perhaps they were just bored.  Anyway I got the usual questions, ASL (which I find to be super annoying by the way).  I informed all the men that the information was in fact in my profile.  I got a lot of, "Oh you're married?" and I said yes.  95% of the men were also married... the question that followed was always the same.... "Are you happily married?"  My answer, "Yes, are you?".  Their answers were normally, "Yes" or "Somewhat"... but what lead after that was, "I"m bored at home sexually.  I want something different."  99% of these married men ended up asking me to lunch, to meet them for dinner or to even meet them in a hotel room.  I'm not talking about 1 or 2 guys here... I'm talking 10+ that did this.  Which lead me to think, I wonder if my husband does this.  Does he think that our love life is lacking and looking for something on the side? 
I would LOVE to say that the answer is no!  But am I sure?  No.  We have a decent sex life - or at least I think anyway, what if he doesn't?
It's alarming at how many men are so willing to throw their vows away to meet a total stranger on the internet for "lunch".  Lunch is code for Affair.  They were all up front about the fact that they want something extra for dessert. 
I will admit that I have been tempted (not by anyone online) in the past to cheat but I haven't.  I think because #1 I have a daughter who I wouldn't risk losing, #2 I love my husband, #3 I fear the wrath of God, #4 my conscience is a bitch.  
I do have to wonder though - what would it take for me to let my wall down and end up cheating - how do people justify it to themselves and make it "ok" in their eyes?