If purchasing (medical! honest!) marijuana legally is more your style than swapping bitcoins over the internet, you may need to change credit card companies: Credit.com discovered that despite it being legal in some US states, lenders aren't so open-eyed, man.
In states that legalised marijuana for medical use, Visa and Discover allow their customers to purchase it using their cards. MasterCard has allowed customers in the past, but perhaps not in the future, saying they're reviewing the policy at the moment. American Express, on the other hand, takes a harder stance on it, claiming that despite some states legalising it for medical reasons, it's still actually illegal due to the federal law.
Medical marijuana depots in Silicon Valley, meanwhile, are already installing NFC readers for Google Wallet payments.*