Earlier this week, in questioning the significance of a "scientists find internet-addiction gene" story, I conceded that the scientific study in question did find something interesting: A gene that seems to be (very modestly) correlated with internet addiction also plays a role in nicotine addiction.
No. Whether heavy internet use deserves to be called an addiction or just a hard-to-break habit is a question about a behavior pattern and its attendant psychological states. To answer it we ask such things as how strong the cravings for the internet are, what lengths a person will go to in order to satisfy them, and so on. But even if we decide, after answering such questions, that a given person's internet dependence amounts only to a habit, and doesn't warrant the "addiction" label, it still makes sense that genes which mediate chemical addictions--nicotine, cocaine, whatever--would be involved.
To see what I mean by this is to see that, yes, a susceptibility to internet addiction (or heavy internet habituation, or whatever you want to call it) is "in the genes" -- but it's in lots and lots of genes, and it's in the genes of all of us.
The reason for this, naturally enough, lies in the process that created our species. Human beings are biochemical machines "designed" by natural selection to, among other things, form habits. In particular, we're designed to form habits that helped our ancestors survive and get genes into the next generation -- such habits as eating meat or fruit or having sex with auspicious mates or impressing people or even gathering tactically useful information about people (i.e., gossip). The habit-forming machinery involves the release of reward chemicals, such as dopamine, that make us feel good upon attaining these goals--upon eating fatty food, sweet food, having sex, hearing people laugh at our jokes or marvel at our exploits, hearing good gossip, etc.