Any substance has the ability to become addictive. I have two ex-friends who were hell-bent that they never had a problem (they would blow $350 a week on weed then tell me they understand what being poor is like...) and one finally admitted that she is addicted to it and when she goes a day without it she starts smoking cigarettes to compensate.

I think it all depends on the person, really. Some people have addictive personalities (I know I do) so I avoid alcohol, etc. Some don't.