I have been running into this a great deal, lately. It ALWAYS hurts. It isn't just that I find professional networking distasteful; I do all sorts of things I find distasteful every day. The problem is that I find the concept fundamentally immoral.
As I see it, cultivating a relationship with another person for the sole purpose of furthering your career is morally identical to cultivating a relationship with another person for the sole purpose of getting that person into bed.
I understand that my attitude is far from universal, and that this behavior is considered acceptable in our society. It is even close to being necessary. But that doesn't change my moral structure, or make me any less unhappy.