When you do it repeatedly and refuse to take no for an answer (like the jerk in my anecdote) that's the problem. Also realize that every woman at a conference gets hit on by about 20% of the men she talks with. At the last conference I attended our marketing coordinator decided to draw a penis on every business card given to her by a guy who hit on her. Out of something like 200 cards, 39 were sorted out into the penis pile.

When you hit on a woman while she's working, you're not going to get laid, you're just going to be the latest in a long string of men making her life hell that day.