Capital gains only apply when you *sell* bitcoins. Tell your friend that you're planning on spending them, and that there isn't an IRS dedicated to Bitcoins yet because we pay a network tax instead and don't have a seastead to start our libertarian government up proper.
you have misunderstood how realization of capital gains works in the united states and similar tax systems. while it is true that if you buy or mine bitcoins you probably don't owe tax until you 'sell' them in most cases, 'sell' in this context basically means 'dispose of'. if you spend $1 to mine 1 coin and then use it to buy something worth $140, you have realized $139 in (capital) income at the time of your purchase.
the same would be true of stocks: if you bought GOOG at $400 in the past and trade it to someone for something worth $800 today, you have 'sold' it for $800 for tax purposes.
