^ all the time. It's even worse with the opposite sex, but the definitions of flirting just seem genuinely different between people.
Recently a friend and I were debating whether it was appropriate if his girlfriend hangs out alone at all with another man, one of her best friends. He thinks not, the act is innappropriate now that she's a taken woman. I think that it's silly to change your ways based on a new and unfounded relationship. The perspectives are neither wrong nor right, just different.
A lot of problems occur though for me, however, when guy friends think I'm flirting with them.. and I am genuinely just being nice. Often it goes over my head when men flirt with me as well, as I don't consider nice behavior and such along flirty.
I'm a pretty blunt person in my own shy way. If I'm flirting with someone, I'm basically asking for sex.. or for a potential date. Anything less than that is nice behavior. Definitely there's joking flirting, fake flirting, pseudo flirting, half-flirting.. I'm running my mouth now lol.
My point is.. no one I date had better be the jealous, untrusting type. They'll be in for a long harsh ride if they are.