An interesting MindHacks entry on why there is no such thing as internet addiction, based on the paper Online Information, Extreme Communities and Internet Therapy: Is the Internet Good for Our Mental Health? (by Vaughan Bell, Journal of Mental Health, 16 (4), 445-457).
His main argument is that "'Internet addiction' researchers conceive of the internet as if it were a set of activities when, in fact, it's a medium for communication." - playing computer games, websurfing and chatting are all bundled together.
Second, people often conflate compulsion with behavioral addiction. By applying such loose standards nearly anything can be termed addiction. Instead he suggests looking more careful at what core problems the 'addicted' have - especially social withdrawal, which is both under-researched and far less cool than addiction. But much more plausible as a problem for 10% of the population than a full-blown addiction.