When I was a sophomore in high school, I was part of a program called peer mediation. Part of our role as "peer mediators" was go around to elementary schools and educate them about the dangers of bullying. My job was to cover cyberbullying. At the time, most of the cyberbullying occurred on AIM. Students would often times create a fake screen name to anonymously harass others. Although this was problematic at times and could lead to bigger issues, it was normally one-on-one harassment.
Today cyberbullying is more serious. It is far easier to anonymously bully someone, and do it in a more public fashion. Facebook allows you to cyberbully someone instantaneously, and what you say can be viewed by hundreds of their friends. There are even certain websites that are dedicated to gossip that allow anonymous harassment. Part of the problem is anonymity. People will say just about anything if they know they are anonymous, can't get in trouble, and don't have to take any responsibility for their actions. Cyberbullying is definitely a problem that has to be addressed, and is occurring in younger and younger age groups.