What do you think about the idea of a "friend zone"? The idea that if one is too friendly to a woman one likes, the woman will only want to be in a friendship instead of a romantic relationship. Apologies if this is a dumb question :S
I'm not sure I really believe that being friendly and showing interest will make a woman dislike you where she otherwise would have been romantically interested in you. I kind of hate the word "friend zone", because there's some resentment implied -- "I wanted X from this woman, but she forced me to accept Y."
Guys complaining that they are "friend zoned" are usually the ones who would describe themselves as a "nice guy", i.e "I'm so nice, but girls only like assholes." There's a weird entitlement there, like the dude is treating a woman a certain way in order to get something (sex) from her.
The way I feel is that if you like someone, you like them; whether a relationship blossoms into a romance takes both parties. If it doesn't go there, then you are friends. If a woman that a guy likes rejects his advances, he has to decide whether he can get over the romantic feelings (for real) or not. If not, it's probably best to move on, rather than pretend to be friends with someone in the hopes they'll suddenly burn with passion for you one day.
Hanging around in the friend zone is bizarre. The implication there is "she doesn't know how good I am for her, but she's gonna realize it someday!" Are you a mind reader? Are you her parent? See, that's creepy.
The myth that unavailable people are more attractive comes from the fact that -self-sufficient- people are more attractive. A person who has his or her own life going on and isn't pining around for love in order to feel complete is interesting, and they will probably be interested in other people with common interests who also have their own lives going on. They will not be interested in a person who eagerly and officiously paying them tons of attention in the hopes of receiving love/sex.
Of course, there actually are a lot of people who only like jerks/unavailable people. They need therapy and you don't want to date them anyway.