There are a lot of problems around proving and prosecuting cases of cyber-stalking. Some of the problems stem from the fact that there is not international "Internet' laws to govern what happens worldwide. Multiply this by the problems of which police agency has jurisdiction and which country will prosecute the case and you can begin to see the complexity of the problem.
In Canada we have clear laws to deal with stalking "Criminal Harassement" and cyber-stalking (264 Canadian Criminal Code). Those engaging in cyber-stalking can face up to a maximum of 5 years in prison. I'm sure that the US has similar laws. It's important to realize that while there are laws in place to protect us there is a great deal we can do to protect ourselves from ever becoming a target in the first place.
Good Personal Safety and Information Security practices will go a long way to keeping you and your family safe and secure. It's important to understand that there is a big difference between the creep who talks dirty to your teenage daughter in a chat room and an abusive ex who threatens to burn down the house while you sleep. We need to take all reasonable precautions to keep ourselves safe, but we also don't want to become hyper-vigilant. I wrote a hub on the topic with more detail regarding what we can do to reduce our risk by using some simple but effective Personal Safety practices