I'm sure you're familiar with alcoholism. Hopefully not from personal experience, since it's difficult enough for those nearby, let alone the person himself. You know, a damaging addiction to alcohol which causes health problems, social problems, and generally fucks up everything.
Somehow that got lost a bit. We created the suffix "oholic" as a way to say "I really enjoy [food/activity]." Let's ignore that this doesn't even make any sense sine it implies that alcoholics are alc-oholics. What is alc?
Someone eats chocolate a lot and suddenly they're using similar wording as you'd use for someone who drinks his life away. The middle-aged woman who buys overpriced imported stuff that is barely distinguishable from a decent local brand (not Hershey's) isn't a consumerist hedonist (the word choice implies more harshness than I intend, but the actual concepts behind them fit). Oh no, she's a chocoholic. She can't help it! Mmm, chocolate!
I'm not suggesting that chocoholics think they have something comparable to alcoholism. The idea isn't there in their minds. But it is in the word. A damaging addiction has been re-purposed to describe something trivial. Addiction in general has gotten this treatment. I suspect much of it is part of a search for identity, for ways to describe oneself quickly, which is pretty stupid. If you can accurately be described quickly, then you're very simple and boring and probably not a very good person in any aspects. If you're not able to be described quickly, then the attempt is a waste of time and only adds misinformation.
Where was I? Oh yes, so shopping addiction, porn addiction, gambling addition; these exist. But the average person doesn't have them. The person who claims to be addicted to shopping is more likely just someone with poor impulse control, too much time, and no concept of credit cards eventually having bills. Again, something crippling has been misused.
The general effect is to weaken the impact and meaning of the word addiction. When addiction ceases to be a physical or psychological dependency with withdrawal effects, when it comes to mean "enjoying something a lot", then it can be applied anywhere. And so we have internet addiction.
Again, I'm not saying there are no internet addicts. There are. They need help. But most people are not addicts. If they seem to have a dependence, it's only because the real world isn't very enjoyable for them to inhabit. The problem isn't the substance or behavior, it's literally everything else. But that's too much to think about, when we can just call ourselves chocoholics and write horror stories about crazed internet youths.