Now that we have virtual worlds, cyberbullies have a new venue to torment people. Take a look at this site, and do a Google search on "cyberbullying". There are a lot of good pointers you can follow to (hopefully) keep your online life bully-free.
The only thing I'd like to add is this: If it does cross over into real-world shenanigans, that's considered stalking, and it's against Federal law. You do have recourse. Contact the FBI.
In the meantime, add your adult voice to the thousands of others calling for a broadening of existing cyberbully laws so that adults are also covered.