There are lots of complexities in the debates about internet "addiction." For those who might be interested, I have an article about this topic on my Psychology of Cyberspace web site ( http://www1.rider.edu/~suler/psycyber/cybaddict.html)
The bottom line for me is this: Is "internet addiction" a bonafide, unique mental disorder that deserves its own place in the DSM... I dunno. Probably not.
Are there people who become so preoccuppied with cyberspace that it ruins their lives, including their job performance and relationships with family/friends.... yep.