I'm going to treat bitcoins as an investment asset until things are clarified. This means keeping track of the cost basis (BTC purchase price + fees) and subtracting the basis from the net sale (BTC sell price - fees) to calculate the capital gain. The advantage is that capital gains held for 1 year have a lower tax rate than normal income. CoinBase provides a CSV export for its transactions as does the Bitcoin-QT client. If your exchange doesn't provide a paper trail, you'll need to keep your own - be sure to include the transaction identifiers so you can use the blockchain to prove when coins were purchased and sold.
Ron
I think this is how it is going to play out. The Coinbase transactions have good records of all the transaction fees and the cost basis. It will be pretty straightforward for those of us still investing, but once I begin making purchases, the record keeping will get confusing because it is not clear to me what the cost basis is for the specific BTCs I will be using. If I could be specific, I would want to use those BTC that were the most expensive to minimize the capital gains, or even to generate a loss. Yuck.