Last month, writer Genevieve Valentine was harassed at Readercon (a science fiction/fantasy convention) by a man named René Walling, a high-profile attendee who told her to stop saying things that "made [him] want to say "wrong" things" and then essentially stalked her throughout the conference in order to "apologize" even though she made it clear she didn't want to talk to him.
I don't know what the answer is in terms of all these guys ever getting it that they can't behave like this, or like the accounts here: http://mariadahvanaheadley.wordpress.com/2013/06/28/but-he-didnt-know-he-was-hijacking-your-ship-on-conference-creeps/
I hate how we have to spend so much effort on how to respond when we are inevitably targeted rather than anyone educating men and policing THEIR behavior. I am grateful for the men like Jim C. Hines and John Scalzi who do speak out, don't get me wrong. We need to clone them.
Speaking about obscene phone calls, this is a thing: if you work on a suicide hotline they'll tell you that once in awhile an obscene caller will masquerade as a sexual abuse victim in order to talk about something sexual while they jerk off. They told us how to recognize them. There were a few known ones in a binder which gave accounts of their usual story lines. My very first night I got one. It is so disgusting to tie up a suicide hot line with an obscene phone call. I read up on them on the internet and ran into a study done that made it clear that the unwillingness of the other person on the line was a key factor in their sexual satisfaction and that they were on one end of a continuum of unwanted sexual behaviors that include rape. So is harassing women at science fiction conventions, groping them and otherwise inflicting unwanted sexual attention on them. Think about that, guys. Get some help.