I think slipknot's problem might stem from the representation. Advertising, and just the media has sooo much influence on the public at large. We don't need these misunderstandings. Non-users will come to think that when you drink alcohol, everyone becomes attractive, get's half-naked, and makes the party happen. But when you smoke bud you apparently snap and start having conversations with bobble heads?
Where's the commercial where the three guys go out for an evening on the town, smoke a couple joints, go to a show, meet some girls, and have a great time without running over some kid at the end?

Having said all that. Sounds like I still would have laughed at Jack in the Box commercial. Haven't ever seen it on though...