I don’t think that everyone who’s hooked on the net is necessarily looking to fill a void in their life, especially young adults. I think many of them started exploring the internet out of curiousity when it was banned. And from there on, they simply became addicted.
There’s so much entertainment available online, so it’s not hard to imagine how someone could get hooked to a point where they stop sleeping/eating/reading/socializing normally and spend most of their time online. It’s addictive and exciting enough, to take over the life of teens/young adults who had pretty okay lives.
It’s true that for many it’s an escape from real life, but I beleive that for many young web-addicts, the cause is not that complicated.