Front page of yesterday's Mail. *Top* source of information, to be sure.
Just because the Mail says someone was bullied DOES NOT mean *all trolls post criminally offensive threats*. I agree with the commenter above who stated that the term "Hacking" has moved from being a descriptive term for anyone who mods/plays around with hardware, to being someone who is certainly up to no good on computers - Black Hat Hacker would be a more suitable term. Online bullying would be a more suitable term here - there *is* a differentiation between "amiable" trolling and bullying. Do not confuse the two (like the mainstream media is currently doing).
The Vulture is quite right - trolling can be as little as a comment meant to drag someone into an argument, an elbow nudge if you will. It can be quite a banter, having an argument online, giving an opinion and watching someone else "explode" due to their own strongly held opinions.
On the other hand bullying, harassment, threats of physical violence - particularly doing so anonymously - are wrong and certainly illegal.
4Chan as a whole cannot be held responsible for all the disgusting things that are written by a subset of people. It's tantamount to saying "London is responsible for all stabbings in the city" - it just doesn't make sense. 4Chan is a sprawling forum of all kinds of wrong, but it is individuals (admittedly coming together and egging each other on) who are causing these issues.
I don't know how I can try to explain it any further. I've trolled. Never anyone who didn't expect it, and NEVER anything violent, nasty or hurtful. Just an opposing opinion worded to bring people into the argument.
The problem with the ongoing bullying issue is that the "trolls" are going out of their way to find vulnerable types to harrass - simply because they know they are likely to get a reaction. Just like the people walking around town who'll kick the shit out of someone at 3am, just because they look like they won't fight back. Wrong'uns.
It's just a shame "trolling" has now become synonymous with the nastier side in the public consciousness - trolling is not a one stop shop of nasty - it's a whole spectrum of actions, some relatively benign, some down right nasty. Don't paint *everyone* with the same brush.