Hold up there...
Wait a second. Yes, we've all heard, ad nauseum, that we're supposed to take it seriously each and every time someone talks about suicide, just like every time there's a short in the fire alarm system. Or the intruder alarm, if you're in the employ of someone who has read the evil overlord list. And we should, in theory. But that only gets you so far in the real world, where your actual ability to take each and every alarm seriously just plain wears out after a while.
See, this is the internet - where threatening suicide is just one more way for lonely, pathetic individuals to bleat LOOOK AT MEEEEEEE into the ether. If you hang out on the 'tubes long enough, you go numb to it. Or start to conclude that it's statistically far more likely to be an annoying plea for empty affirmation than anything else. And it's not like people haven't faked their deaths on live webcams before, either (were you there when Jay Stile did it?).
So I'm sure there were some sickos chortling as this guy died, but on the other hand, I suspect a lot of the viewers honestly and reasonably thought it was a put-on.
Also, were 1500 people watching the whole event start-to-end? Or is that just the number of traceable IP addresses that viewed the stream for any measurable length of time at some point during the event? This guy looks like he has a webcam pointed at his bed - if so, how many people tuned in, saw some guy apparently asleep, and tuned back out without ever thinking anything further about it?