Aren't these cryptocurrencies inflationary? As I understand that it, mining these cryptocurrencies does not create any real value, so basically, a fan cryptocurrency has a value, this means that the value of the currency we currently own is devalued. Right now, the total value of the crypto currency creates an s probably still too small to matter, but if it becomes significant, there should be an inflationary impact on the economies.
I also think that the government eventually will crack down on this for above reason and the ease to use it for money laundry. Sure, the government mayn't be able to control who owns it or who uses it, but if they make the use of he cryptocurrency unlawful, then the cryptocurrency would become a Mafia currency of some sort and be worth far less for most of us.
I think it is just a matter of time when this get regulated to some extend. This is now like the "Wild West", but eventually, the Wild West was ruled by law as well.