Is the appreciation in bitcoins taxable? If you have large gains in bitcoin, is there any way that it can be taxed?  If I have $5000, and it appreciates to $10,000 worth of bitcoin, when I sell bitcoin for dollars can it be taxed as a capital gain?  I would think that since there is no documentation to support it that it would be difficult.
My guess is that as long as you have a receipt for the buy, and one for the sell then there is no reason why the government would say no to taking their share if it. I guess it's just classed as currency trading??