Depends on your country of residence mate. Some countries do not accept any transaction in the form of bitcoin and to do so in such countries, you go by illegal means like in US, I think you probably need a money transmitter license for larger volumes and in Germany its legal but you have to pay tax. If you don’t pay tax you will probably get some trouble.

Well, I think of it that bitcoin will not ruin a country, Just take a look the positive side it brings, bitcoin is providing good opportunities to its people for investment and trading and also the transaction which made through it is cheaper and faster, so bitcoin can be a good tool to make country financially strong.

The reason behind its constant increasing in value is that, it's a digital currency any transaction/purchasing which made through it, is totally secure and hidden, no one knows the identity of transactors/buyers.