For digital-marketing agency Cooperatize.com, taking bitcoin for payment was easy enough. All co-founder Roger Wu had to do was obtain a digital wallet. To promote the move in 2014, he even penned a blog post for Forbes explaining the decision.

The number of transactions the New York-based firm has made since? Zero.

"The biggest thing is, are people willing to pay in bitcoin?" Wu asked. "The reality is that most of our customers are other businesses and other businesses don't use bitcoin."