First off, I hope somebody somewhere feel bad about themselves. Using others misery for your own entertainment is pathetic. That being said, there is a subtle but important difference between the two cases you mentioned, in the first one, the victim was driven to suicide as a result of psychological cruelty and manipulations from somebody who intended to do that, make somebody suffer. In this case, the guy had apparantly (without knowing more than is posted), tried suicide before and as such, has a history of mental instability and was suicide prone over something that had nothing to do with the people on the net. Of course, a swathe full of jerks in a public place doesn't help, but it seems more like the symptom than the cause (unlike the first case). Rule of thumb, get a life outside the internet and don't trust strangers, even if they use smilies.
Edit: I always thought it strange how low people can think when hiding behind the anonymity of the net. It's almost a mob mentality where the collective IQ is the squareroot of the lowest one participating.