Starchild, nice post!
"Compared with subjects who had used less than one joint year, the risk for lung cancer was ... 0.74 for 10-30 joint years, ... A risk below 1.0 means that the risk for cannabis users was slightly lower than for non-users."
This tells me that the optimum amount of majuana smoking is about 15 joint years. That would be about 5,000 joints. That's a lot of dope, way too much as a prophylactic. The real problem with marijauna is that it affects one's mind long term (which is why people smoke it in the first place, short term). But if we can ask "whose body is it anyway?" we can similarly ask: Whose mind is it anyway? I suspect that most drug use including and especially alcohol, is self-medication for the mind (including "physical" pain); same question applies.
But there's a principle here. A little of almost any poison is good for you and you are better off with that poison than without it, even heavy metals. The question is always when too much really is too much. The government regulators are oblivious to this principle. So it's always a trade off whether prohibitory regulation does more harm than good even as to the effects of the regulated substance, let alone all of the unintended consequences (e.g., organized crime in the case of prohibitions).
PS re "gold" I predict hyperinflation. Jeff Hummel says it will work itself out as a massive default by the US Government on its debt (such as it did when it invalidated the gold clause in 1933). They amount to the same thing.