So what you're saying is guys typically only flirt with girls with the intention of getting in their pants. Thanks for the insight. So now when some guy makes a flirty comment to me, I know he's not trying to be flattering, he's seeing himself pursuing me for some sort of longtime relationship and now I know I have to tell him to go fuck himself or else he'll think I feel some romantic feelings towards him.
I actually think this is a pretty good way to go

From the first line of the wikipedia article on flirting:
http://en.wikipedia.org/wiki/FlirtingFlirting is a playful, romantic or sexual overture by one person to another subtly indicating an interest in a deeper relationship with the other person, and can involve verbal comunications as well as body language.
I guess the term "deeper relationship" is what needs to be defined here, but yes, if a guy is flirting, TRULY flirting, they're either trying to get in your pants and become your boyfriend. I don't think there's any way around it.
I definitely find myself "flirting" with nearly any woman who comes across me. I always thought I was just being polite and charming... but it seems everyone else calls that flirting. I can say that 98% of the women I've flirted with I had NO interest in getting in their pants.
If you don't consider it flirting, then you're NOT flirting.