"The fact that you have to do your business in the shadows works out for the best--it certainly does not prevent use and abuse of marijuana (case in point, you), but it does place a barrier of forbidenness that MOST people will not cross, thus limiting the level of use and abuse."
That's actually not true. According to the SAMHSA's National Study on Drug Abuse and Health, more than half of all adults born from 1954 on have tried marijuana. Since the early seventies, most young people have crossed that "barrier of forbidenness."
See Table 1.2B:
http://www.oas.samhsa.gov/nhsda/2k3tabs/PDF/Sect1peTabs19to27.pdf
Note: These numbers are probably low because each year somewhere between 25% to 50% of the people they try to survey do not respond and people who do respond in many cases probably are not entirely honest about illegal activities they have engaged in. Studies have shown that something like 30% to 50% of people surveyed underreport tobacco and alcohol use. It's probably worse for drug use. But, people are more likely to admit past use from years ago than they are to admit current use.
Since it is impossible to verify that "more than half of all adults born from 1954 on have tried marijuana"--since you yourself stated "...people who do respond (to surveys) in many cases probably are not entirely honest about illegal activities they have engaged in"--I'll take those stats lightly.
If they're true, perhaps I should have said "crossed the barrier of forbidenness and STAYED"?