As I see it, problems resulting from cannabis use have four major sources: first, there are dangers in the plant itself (in cannabis alone these are few); second, there are dangers resulting from human modification or concentration of the raw plant medicine ("pharmaceuticalization"); third, there are dangers resulting from improper or irresponsible use by the consumer; and fourth...
As with all drugs (and anything in life really, from driving to skydiving to simply existing), cannabis comes with potential risks and side effects. Thus, in order to maximize benefit and minimize risk, good drug education includes cautions and warnings of potential risks and side effects, as well as basic standards of use.