Here in the U.S. it is taking off by the billions. The rest of the world, I'm not really sure. If you want to buy a domain name related to this industry, should it be an "American centric" name and extension, or something that has a worldwide appeal?
Tigger, you absolutely know that this is taking off in the US, however, India has different laws about that kind of thing. I suggest that you do some research to avoid issues for yourself. There could be some real bucks out there in the world if you position yourself correctly.
Someone once told me that there'll come a time when cannabis will be legal the world over. I don't know how true this is or how long it will/might take but as @Abhijit states, you may want to research more before settling on such a domain name.
I flipped one marijuana (.com) domain name in 3 months for a 3000% profit. I think I was just lucky as I have not been able to repeat that again. Still trying but be careful what you buy. Just because it has "marijuana" or "cannabis" in the name does not mean it will sell and it definitely will not sell in extensions or countries where it is illegal!
I believe that legalization will eventually happen but with regulations that equal revenues to the ceiling. Already, the parent company of Bayer Asprin has copywritten some names that they plan on using once they can sell to the general public. I hope that big pharma doesn't ruin the marijuana market like it has other drugs and supplements. You know what happened when Ma Bell tried to become a monopoly.