It depends on the way it is used. The internet is a great tool, resource, and outlet, but like anything if it's used incorrectly it doesn't fulfill it's purpose. How it should be used depends on the person I think as well, but in general the more things one has going om outside the internet the more useful the internet can be to a person. I mean if you spend 8 hours a day on the internet, but have a lot of other things going on during your other waking hours, the internet can be great. Or if you only spend a few hours a day but don't really have much else in your life it can be more harmful I think.
The less major a part of your life the internet is the more useful it can be basically. As long as you're living outside the internet it can be good, otherwise you're lost. It's just a part, and like everything needs to be in moderation and proportion.