The bankers teaming up with the government. Once they combine forces then digital currency suffers. They know that users of cryptocurrency are still vulnerable because it is new so a rumor or news spreading FUD would have a big effect in the price and we have seen it recently. Bankers and the government in China decided to ban crypto trading in their country because financial institutions are threaten by it so as a protection for them, government bring up licensing so that they would still have control. Bankers losing their business and government losing their control would be the worst enemy of bitcoin.