The only way I'd call it cyberbullying is if a bully who's been hassling another kid in school.  Then went online, seeked that same kid out, and continued to torment him.  And if that happens, that's a kid with WAY too much free time, and WAY too few hugs from his mommy.

Trashtalking is just one of those things which will always happen.  I know with the people I play with, that the trashtalking is just for fun, and if it goes too far I can just say so, and they'll slow it down a little.