I think you and I have different meanings in mind for the phrase "hit on". If I'm at a conference and meet a woman I'm attracted to (and likely has similar interests since she's there too), why would it be bad to try to get her phone number? I may never see her ever again.

Below you talk about "not taking no for an answer". I don't call that "hitting on", I call that pestering and, yes, that would make someone a dick. But in my opinion that makes you a dick no matter where you do it, not just in business scenarios.