i here-fore intend to nullify of validity all comments in this discussion based on anecdotes or otherwise personally observed "people whose lives were ruined by weed". for those of you who fail at common sense:
assume NINETY FIVE PERCENT OF PEOPLE ARE MORONS. 95% is my personal opinion, you may have your own, but it's not important for the amazing revelation awaiting you in the next paragraph. your mind will be blown by this incredible basic math.
also, assume TEN PERCENT OF AMERICA smokes weed often enough to be "a stoner". this i do not know to be true, but you can substitute your own number below, because pretty much any figure between 1% and 100% will yield a meaningful value from this fantastic knowledge-bomb.
THE FORMULA:
Q1 -- IF 95% of all people are morons, AND 10% of all americans smoke, THEN what percent of STONERS that you meet WOULD YOU EXPECT TO BE morons?
A1 -- 95%. not knowing for certain what marijuana really does to you (nobody here knows, hence the discussion), you would expect 95% of the stoners you meet to be just as dumb as everyone else.
Q2 -- IF 95% of all people are morons, AND 10% of all americans smoke, THEN what percent of EVERYONE that you meet WOULD YOU EXPECT TO BE a smoker who is not a moron?
A2 -- .5%, about one in two hundred people. assuming the average american has about 300 facebook friends, it's safe to say everyone probably knows an average of 1.5 guys who smoke weed and are still fully functional people.
Q3 -- IF 95% of all people are morons, AND 10% of all americans smoke, THEN how many SMOKERS would you need to meet before you'd EXPECT to find a smart one?
A3 -- twenty. if you know twenty stoners, nineteen of them are probably morons.
so there you have it. anyone saying weed is bad because "{1 .. 19} people i know ruined their lives on weed" should be ignored because they don't know enough stoners to have a valid opinion of the effects drug, and if anyone were to say they know more than twenty people who've "gone to pot" sic then they are probably omitting, forgetting or lying about stoners that they know who are still intelligent.
in short, leave it to the fucking studies. and right now, there aren't a whole lot of studies on weed that are both unbiased and well-designed experiments, mostly due to government regulation.