Up to 30 percent of South Koreans under 18, or about 2.4 million people, are at risk of Internet addiction... They spend at least two hours a day online, usually playing games or chatting. Of those, up to a quarter million probably show signs of actual addiction, like an inability to stop themselves from using computers, rising levels of tolerance that drive them to seek ever longer sessions online, and withdrawal symptoms like anger and craving when prevented from logging on.
To address the problem, the government has built a network of 140 Internet-addiction counseling centers, in addition to treatment programs at almost 100 hospitals and, most recently, the Internet Rescue camp, which started this summer. Researchers have developed a checklist for diagnosing the addiction and determining its severity, the K-Scale. - NYT, Sunday, 18 Nov.
You can check your level of Internet Addiction here.
Some more background. Moral: Be aware of unintended effects.