The cobra effect is when a policy (usually from government) is supposed to solve a problem but ends up making it worse or creating a totally new problem.

The name comes from the British government in Delhi, India who wanted to rid the city of venomous cobras so offered a reward for every dead cobra. This was initially a success but then locals started to breed cobras before killing them for more income. The government found this out and scrapped the reward. The breeders released the cobras into the wild creating more snakes than the original problem.

I often think about the cobra effect when governments talk about banning or controlling Bitcoin.