OC:: internet bullying

i guess this is the first topic that came to my mind to write about this week, due to my recent encounters with negative/hateful/offensive comments being left on my personal blog. the comments were anonymous and not linked to any username, so i assumed it was a random "troll" and disregarded what was said. in the beginning, i just deleted and ignored the comments, but when more personal attacks came, i found it amusing to counter and respond.
my first instinct was that the person was spamming me because someone who didn't like me posted links to my page on a site and told people to send me hate mail/comments. this made sense because the person seemed not to know me very well, although they were armed with some personal info/rumours about me. their IP address also linked them to illinois. i don't think i know anyone there.
after a full day of genuinely having fun chatting with my pseudo-stalker and egging them on [note: i know it would have been best to delete/ignore it, but it was actually interesting to try and sleuth the identity of the person and to test how much they really knew of me], they revealed their identity to be someone i personally knew in real life. someone who had never before given me any indication of their distaste for me, and someone i had never personally wronged, nor had i hurt anyone close to them. he continually insisted that he knew that he was getting to me when in reality, like i said, i found the situation to be amusing. here's a quote to help me pose some questions for you to ponder:

"Keep crying about me, telling yourself your feelings aren't hurt...you know that it just fuels my fire."

"I know that I'm under your skin and I know that I'm in your head, and I know that I'm hurting you."

pretty ridiculous.
i guess i just want to ask everyone's opinion on internet bullying. why do you think people do it to begin with? out of personal insecurity?
why do people think it's an acceptable way of communicating a negative opinion of someone?