On a related note, a merchant could probably easily hide all evidence of having received bitcoins, and then record any product dispensed in return for those bitcoins as a "promotional giveaway", deducting the "forgone income" on their taxes. Not recommending it, but I don't know how they'd enforce this if the buyer didn't say anything...
Yes, but the income from selling the bitcoins on the open market is still taxable. You might be able to argue it is capital gains instead of income, but then you have to prove when you acquired the coins.