[nicklaf]

Point taken; you are right to defend the drug comparison, so long as we're talking about compulsive behavior with negative effects.

I do feel the analogy is overused though, mostly because the notion that chemical reactions in the brain are involved seems to have an unduly strong impression on people, whereas I imagine that these phenomena in the brain turn up in all sorts of human activity (see sandworm101's comment).

There's also a negative connotation that exists with drug usage. I could be totally addicted to jogging, though ("runner's high"), with an almost totally net positive effect on my life.