If you are a established company meaning you own a big amount of BTC and you render a service then you should pay your taxes based on your income as any other company. Any activity that generates a profit should be taxed, furthermore, exchanges as an example who are holding very large amounts of capital are at the aim of the governments. Taxes would be a middle ground between the dark and anonymous cryptoworld we are now and the world of the future where you can buy anything anywhere using a digital wallet.