"He's totally honest with me."
"He'd never even think about cheating on me."
If you think that? And I don't care how in love you are, or how much he loves you (he probably does love you, in fact) you've not really lived life.
All men are guilty of it. They need the affirmation too badly. If they say they'd "never" they WILL BE the first ones to do it.
The same goes for women. Women just don't talk about it as much, nor get busted as often.