I would like this because some guys attempt to 'chat me up'.. but I'm a guy lol.
Though it should be optional for those who would prefer to stay anonymous and I don't like the idea of any additional 'features' of such which change depending on the gender you select (like the name colour suggestion on the first page - because I personally prefer pink over blue, I don't agree with such gender stereotypes).
Reason for making it an additional profile field rather than having people fill it in themselves in other profile fields is the fact that the latter may cause people to assume you're seeking attention (like a misconception with 'gamer girls')
I really don't like people who will only talk to those of which are potentially the opposite sex in hopes of finding romance from it, it's pretty sad.
If all you're seeking is romance, go to a website intended for such, don't strive for a relationship in a game.
Of course it is possible to find a relationship through a game (met my gf through a game), just don't make it your only objective, that's just creepy.