yeah, that is something that is completely subject to each and every different relationship. you have to set those boundaries in your relationship. what one relationship might consider harmless flirting (I don't care what he does b/c I know he's going home with me), another relationship would end over it (she looked in the direction of another man!!!). Tailor your boundaries and limits to your own relationship. =)
Even after setting your boundries I would tred lightly. What one person thinks he or she can tolerate and what they actualy do can be two diffrent things. I would like to think that I can handle almost anything but there are times my fianc'e and her flirting sting a little. It's not a trust issue but some times you just feel like, hey I wish she still flirted with me like that. Hmmm somthing for us to write about on our web site LOL.
I'm with the others on this one....each couple will have their own boundaries....and it is something that should be discussed, and subject to interpretation etc.....I like what immortalone said, he wishes his fiance flirted more with him....sometimes that's important to remember when married, keep flirting with each other!!!!!