As a freshman at the University of Notre Dame looking at business, economics, and finance as a possible career route, I couldn't help but draw some correlations between the idea of economic models and the dating scene here and possibly at other colleges. In my opinion, you can simplistically model dating and social life as an economic trade. In this sense, young men generally trade emotional support for sex, while young women generally trade sex for emotional support.
If you trade fairly then you have a happy relationship, however when ideal market conditions do not exist, this is where the concept of "nice guy" doormats and "easy girl" sluts come into play. If a female offers the sex too cheaply (i.e. without demanding emotional support in return) then the market value of her product goes down. In turn, uncaring men (aka jerks) will take the sex without giving back emotional support -- this is the stereotypical "easy girl" who only gets invited to frat parties because she puts out easily. Conversely, if a male offers emotional support too easily, then the market value of his product will also go down, and insecure women will take all the support he can offer without having to offer back sex... (at most, he's likely to get some odd bit of flirting as compensation for his product). This is the stereotypical wimpy "nice guy" that girls say "If only he were like you" to. These kinds of guys are kept around and minimally flirted-with because their product (compliments, emotional support, attention) is useful and easy to get. However, a female will never sleep with this kind of male because: A) His product is offered at way below market value, and B) She doesn't take him seriously enough to consider him a potential mate.
It's a cold, sterile model which obviously doesn't capture all of the nuances of socializing and dating for a second, but nonetheless, I believe it is a compellingly simple model that explains the basic idea of "nice guys" and "easy girls" alike. The lesson to be taken from this economic model is that niceness could pay, provided you are NOT EXPLOITABLE. If you price your goods or services too far below market value, nobody will recognize the real significance of what you're offering, thus by extension, they will not value you. More importantly, they won't stop exploiting the use of your services or goods. People will almost never voluntarily pay more than you make them pay. My guess is that, while oversimplified, this is more right than wrong, i.e. a handy way to look at things.