I feel really sorry for you Americans, are there no amphetamines over there? (Meth = shitty speed, not pure at all, and gives you a LOT more sideeffects). Speed (amphetamine) is much more fun, much more safe, and was even used for decades by the military (not only pilots).
YOU AS POT SMOKERS should know a lot of drug-info out there is propaganda. So is it with hard drugs too. There is no drug I am aware of that makes you immediately physically addicted (yes, I'v tried Heroin).
That said, if you are unsure - don't do it. If you find yourself smoking weed from morning to evening every day - even if you think you need a break, then you know you have an addictive personality. Stay away.
edit: Oh, and did you know crack is simply "dilluted" cocaine? That's why it's cheap.