Cryptocurrency, of which Bitcoin is merely one, is one of the biggest displays of idiocy in the history of mankind. Really. And then I'm being rather nice about it, to be honest.
The bitcoin came to rise to fame out of distrust for the regular financial systems, and let's be frank the 2008 world economy crisis show that distrust was justified. Yet, regular money, like dollars, euros, pounds, and so on, do still have some authority checks and even authorities standing in a kind of guarantee. The bitcoin has none of that. No do other cryptocurrencies have that for that matter.
As a result the cryptocurrencies are like a gift from heaven for criminals. Police cannot trace it, so it's very easy to ask ransom in cryptocurrencies, in order to be traceable. Same goes for money made with drugs deals. And cryptocurrencies are also very easy for money laundering. Oh, and how about avoiding tax. We all hate paying tax, but if you realize how your country would look without tax.... rather not think about it.
Not to mention how much the value fluxuates. 1 bitcoin has been worth more than $1000 each, and also less than a few cents. Such instability is lethal for economy and can lead to nothing but trouble. Of course the complete lack of control by authorities make this coin fluxuate a lot.
This being said, I only mentioned the tip of the iceberg. All this can only lead to undermining the existing financial system eventually leading to a crisis that will be unstoppable.
Many countries are investigating if they can ban cryptocurrencies, but unfortunately, the law is not capable of succesfully banning this. Especially since they are not traceable, you cannot uphold such a ban. One of the many weaknesses of the internet. And banning something while you have no means to actively get people who violate the ban sued, it pretty pointless.
If I were a criminal, I'd love cryptocurrencies. Anyone who has no criminal interest is advised to stay away from that.