Alcohol is the only freely available mind altering drug (well in UK at least). More accidents, injuries and fights are caused by it than any other single factor. It also contributes to liver disease, obseisity and many other illness's that are proven to be directly related. I think one of the worst problems with alcohol is it realy is too easy to lose track of just how much you are consuming.
Alcohol doesn't change who you are as a person, what is does is take away your inhibitions, inhibitions are what make us a civilised society, its what stops us saying what we realy feel inside, acting out our emotions in a negative and sometimes positive way. Obviously alcohol also slows us down, our reaction times are slower, our vision is impaired and that when accidents happen. I am far from an advocate of drugs, i am strongly against them, but in the case of weed there has to be an argument that comparitevly speaking its effects are less harmfull.
I think that both stimulants used with caution are relatively safe, if only people were willing to be more cautious of there intake for their own saftey and others.