By no means am I saying I would or wouldn't I am more undecided on the whole thing I can see it from both sides. So maybe not justifications but reasons you may say yes.
1. The excitement of being sneaky and not getting caught
2. The thrill of going out to look or meet someone or on the hunt for them.
3. You wouldn't get caught.
I've been/done all three. and I have to say that depending on the circumstances the last one is fun. But i'm only saying that b/c the two times that happened with me I really didnt like the other girl and I was doing to "steal" her boyfriend, weather I liked him or not. So it came out fun for me (ahh...middle schoool times").
But now that I've grown up just a bit, i'm going to say "no" I wouldnt again. Seeing whats going on with my mom and my dad has made me realize that weather you get caught or not, its not worth it. In the end, your going to be hurting your spouse, yourself, and the other person.