The only thing that i see danger in cryptocurrencies is the government because if the government will not agree in using cryptocurrency then if they will ban it then our hard work will turn to nothing so i think it is better if we make using cryptocurrency legal first so we don't have to worry about because the coins are legal and the government already approve it.
I dont think government will have any issue with it or it takes down any cryptocurrency.
I think the main problem that a government will have from it is that it is difficult to imposing tax from bitcoin but if bitcoin will make some changes for them in its rules it will be acceptable by them.