I have actually been interested in a guy before and not known he was married. BUT...as soon as I found out (he was not sporting a ring, btw) I backed off. I would f'n KILL my husband if he did that, so I will not do that to another woman.
A married buddy of mine says he gets hit on more by women now that he's married (his in his mid to late 30's). And the women are more aggressive about it. He said he thinks him being married makes it bigger challenge or a greater conquest for these chicks.
I still think it comes down to an integrity issue. Might be kind of a kick to "tempt" a married person just to see if you can get them to capitulate, but anyone who would shit on their partner like that should just not be married.
Why is it the people closest to you are usually the peopel who get taken most for granted???