Bitcoin as an alternative payment system is theoretically good for any value transfer in any industry. I say theoretically because there are a lot of constraints that impede its adoption, of which regulation is probably the most significant.
The uncertainty and controversy around Bitcoin would be highly compounded if it were used as a solution for the Cannabis industry. In fact, it already has proven lethal for at least one a company that was unable to reaise VC money in spite of having a great team and product.
A lot of things that are hard to change -policy, law, regulation, law enforcement attitudes- would need to change for this to be a viable combination. Of course, entrepreneurs always have the choice of ignoring these concerns and ask for permission and deal with the consequences after the fact.