I'm not sure about Australia, but in the US there has been a lot of decriminalization over the years regarding Marijuana. There are a lot of claims that it is great and a cure all. The science does not back this up. There are benefits that have been seen, but not the cure all that some make it out to be.
What does seem to be true of the claims is that there are no known long term side effects. There are some mild ones I think, but nothing worse than alcohol. And the short term effects seem much more mild than alcohol. On another note, there is no known long term side effects for LSD either, and like Marijuana, it's not addictive. Although, the short term is much different for LSD.
If you're interested, here is some good reading on the science behind cannabis being the cure for cancer:
Cannabis, Cannabinoids and Cancer – The Evidence So Far | IFLScience
Probably worth mentioning that I have never used either of these drugs.