I believe that Marijuana would be fine legalized, although it would still need a great bit of control. The main reason being that, obviously, second hand smoke could get unwilling or unknowing bystanders high (I wouldn't mind :3). Obviously, like stated before, taxes from this would provide HUGE revenue, likely shrinking the US' huge debts.
Perhaps smoking it would be confined to certain areas of a place, such as bars, or smoking lounges.