What the internet's done is it's given people a medium to say whatever they want to or about whomever they want, and they no longer have to do it face to face (or even voice to voice). They can even do it under cover of complete anonymity. And since they can't physically see the person the person they're doing it to, that person becomes more or less a cardboard cutout. Basically it's turning people into virtual psychos who are drunk on the power that comes from knowing that you can have a damn good pop at destroying the life of others from the comfort of your own keyboard.
It's not just comments on blogs and forum, business owners are feeling the brunt of this too. When I started my current business about 10 years ago, online business reviews weren't so common: Google didn't have them and Yelp was a twinkle in the eye of its creator. When I had a dispute with a customer, it was more or less done either in person, over the telephone or via email. In other words it was a one-on-one affair. Now, people get into the most trivial of disputes with me (a contested $5 surcharge on their bill for instance) and it's not enough to have a civilized discussion over the phone - no, they're threatening to go online and ruin my reputation. And some of them do it too! They go straight onto Yelp and write fake reviews full of outlandish fabrications and baseless personal insults. I've had to threaten people with legal action. Recently I had a woman who had the most ridiculous beef with the service I provided, and she went straight onto Yelp and posted 3 fake reviews in quick succession under fake names calling me a psycho, don't trust this guy, his company is totally shady etc. I had Yelp remove them because they were so ridiculous, so she started posting more. It got to the point where I had to find out where she worked and call her boss because she was doing it in office hours, no doubt on her work computer. Over the matter of a few dollars, she quite seriously wanted to ruin my livelihood and that of my employees. One bad review online can cost you tens and sometimes hundreds of thousands of dollars in lost revenue and cause people to lose their jobs.
But that's nothing when you consider that kids have been bullied to death on Facebook.