Be careful, the after effects can be worse than having a physical addiction to a substance. When you are addicted to alcohol or tobacco you're physically harming yourself, either from the smoke inhalation or liver damage; however if you were to stop drinking/smoking at twenty-five then by the time you were fourty/fifty there would be no signs you were a smoker/drinker (source BBC News a few nights ago lol) - this does not include cancer cases from smoke damage/liver damage, of course. In the case of a "virtual" addiction you miss out on the fundamental building blocks to life, such as social skills, and you don't even know it.
This isn't your standard nerd, this is the person who doesn't go out for three weeks and just sits on the PC or watches TV all day; they live in their own world. It's similar to the porn addiction, many teens don't know it but they're not having sex because they're watching too much porn. I'm definitely not saying this is you, but it's an interesting concept to be addicted to the virtual world.
Before you reply to this please bare in mind this is just what I've found from the documentaries I've watched on addiction and from the books I've read, if you disagree you don't have to be abusive; it's possible to have a discussion and walk away feeling like you've learnt something, the key is not being a dick.