Do men know when you are flirting? Are you too subtle or are they too blind? Chat amongst yourselves...

I have heard a lot about men being thick and men not noticing when a woman is interested.  I can fully see both points of view.  When I was in my teens and early 20s, I had women interested and flirting with me but had no clue.  Some because I didn't want to have a clue, others because...well, their idea of flirting was just too subtle or unfocused.  Now I'm a lot better at telling.  Maybe it's maturity or experience?  Or maybe women are just flirting differently?

Watching women flirt on the other hand, with someone other than myself, it's quite obvious.  Sometimes I'll notice someone flirting with me and catch on but for the most part, if it isn't obvious, you may as well be talking to a wall.  Now some women go overboard with flirting to the point of being creepy.  For instance, I was out with some out of town friends and walked by a woman who almost touched noses with me and did some kind of flip with her hair that I just ignored because it was too much, she was obviously under some influence and with a guy (I later found out).

I'm aware there are different reasons to flirt and all but that would only be for women.  Men have only one or two reasons to flirt and that's if they know how to. 

Is there a huge gap in the way women flirt than men and who is more effective?  Can men tell right away when you're flirting or do you have to make it more obvious?  Guys, is it easier to tell someone's flirting or are you just more perceptive than when it's not you?