oh and another point. you dont pay tax until the point you have FIAT in your hand. so dont think that if bitcoin rose from $450 to $470 in one day that you need to send a payment to IRS at every price movement, simply because your holding coin instead of spending..
point being... its not a gain or loss until its FIAT!!
For miners, the bitcoins mined are now taxed as income using the market price at the time of mining as the basis. Even if you never sell the bitcoins.