A few marijuana facts obtained from link.

"Tetrahydrocannabinol is a very safe drug. Laboratory animals (rats, mice, dogs, monkeys) can tolerate doses of up to 1,000 mg/kg (milligrams per kilogram). This would be equivalent to a 70 kg person swallowing 70 grams of the drug -- about 5,000 times more than is required to produce a high. Despite the widespread illicit use of cannabis there are very few if any instances of people dying from an overdose. In Britain, official government statistics listed five deaths from cannabis in the period 1993-1995 but on closer examination these proved to have been deaths due to inhalation of vomit that could not be directly attributed to cannabis (House of Lords Report, 1998). By comparison with other commonly used recreational drugs these statistics are impressive."

Source: Iversen, Leslie L., PhD, FRS, "The Science of Marijuana"

Alcohol alone kills more people annually-- no, strike that, EVER-- than cannabis, and this is NOT because fewer people use cannabis:

"Marijuana was first federally prohibited in 1937. Today, more than 83 million Americans admit to having tried it."

Sources: Marihuana Tax Act of 1937

"According to the UN's estimate, 141 million people around the world use marijuana. This represents about 2.5 percent of the world population."

Source: United Nations Office for Drug Control and Crime Prevention, Global Illicit Drug Trends 1999

The Netherlands have legalized cannabis. As far as I know, there have been no complications with drug use in that country since the laws changed.

And finally, if Law and Order SVU has taught us anything, it's that the only reason marijuana was outlawed in the first place was because William Randolph Hurst and his paper mills were threatened by the hemp industry. ;o)