You don't buy weed with a bank account unless it's off the dark net. And how would you freeze their account? Call the bank and go 'yeah so and so didn't give so and so their weed'
I know, but I am talking about when marijuana is legalized in more states. Maybe opening some sort of agency that stores your pot for you or just a company that manages liabilities for pot growers in states where the drug is legalized, as theft of marijuana is a pretty big thing. I mean, like with any asset - there is tons of liability.
Also OT: but while I am not necessarily a proponent of the drug, I see marijuana becoming the next cash crop. I'd have no problem whatsoever getting involved with it (not using it though) but forming some sort of marijuana-based company or investing into a company.