Personal Space

I went to a networking event last night.  You know what's worse than a guy (you are totally disinterested in) who won't stop talking to you?  A guy you are totally disinterested in talking to you and encroaching on your personal space.  I must have backed up 10 feet.  He decided to come closer every time.  Why, oh why?  I would have been really unpleasant had he not been a friend of a friend.