When I first went online I became almost instantly addicted to the Internet. I went from being a guy who lived on a little ranch out in Fresno county (my nearest neighbor was 5-miles down the road, the nearest city 26-miles away), who only had his dogs, a few temperamental cats and assorted other critters to talk with, to someone with the world at his fingertips. With a few clicks of the mouse I could discuss the latest news with someone in England or Israel. Instead of the local newspaper, I could scan newspapers from Moscow, Jakarta, Cape Town, or Cairo. It was just so overwhelming that I spent every free moment online. So much so that I would forget to cook dinner, clean up around the house or mow my lawn. Friends could never reach me because my phoneline was always plugged into my PC (I had AOL). Everybody started getting mad at me.
It was my mom who told me that my Net addiction was really a bad thing. That got me to thinking, and I forced myself to walk away from the Internet completely for months. I canceled my AOL service, boxed my PC up and just forgot about it.
And when I came back, I had licked the compulsion to spend all of my time online. Now that I care for my sister and am paid to do so, I spend a lot of time at home. So in the typical day I may be online 3 hours max altogether. Which is still a lot, I guess. And I have insomnia (since childhood), so when I'm awake in the wee hours I'll come online and whittle away some time at Christian forums or reading newsboards.
I think anything taken to excess is bad. Especially if you get in as deep as I was, basically forgetting to take care of yourself because you don't want to step away from the PC.