Actually, that was poor wording on my part. It's not a drug. But it - and facebook - and most of the new social apps, are designed by sociologists and psychologists who study the sociology and psychology of addiction. They want to mimic the experience of addiction.
They also study the sociology and psychology of love - how we fall in love, etc.
All of its transmogrifying into a field they are now calling gamification. It grows out of the old Human Computer Interaction field. Because humans, when confronted with a machine that responds to their behavior, treat it with the same rules they expect in social life.
Like you and ravi, I'm not opposed to social networking sites or anything. I don't think they are a priori a negative influence on human life. So, don't get me wrong. Probably the best way to look at is that it's a form of phatic speech. Especially Twitter.
I also have little patience for the other side which unqualifiedly glorifies this technology. Corey Doctorow for instance. No such luck that that guy is sitting shamefaced about his claims about how wonderful crowdsourcing is. Or, that King of Free, Chris Andersen? No such luck that he's embarrassed about his stupid ass book about how everything is gonna be free, whee!