It's not rocket science. If I grow pigs, when I sell one, I pay taxes on the income less expenses for raising the pig. Likewise, if someone mines bitcoin, when they sell it or buy something with it, they pay taxes on the income less expenses to mine it.
If I invest in pork belly futures and later sell them at a profit, I pay taxes on the capital gain. Likewise, if I buy bitcoins and later sell them at a profit, I pay capital gains on the profit.
Any CPA worth her salt should be able to calculate what you owe in taxes as long as you keep good records, as the law requires - no?
Yes, I understand more than you can imagine...and when the IRS has a couple of bitcoin audits producing adjustments to income, congress will gin up a slew of regulations to "help" the taxpayer comply. Don't think vendors that deal in bitcoin will not be forced to surrender the names of their bitcoin customers. Forms 1099-B,C,MISC,INT,DIV,R,S are the products of the evolution of various "systems" which are now compelled to report with "good records". Bitcoin will be just as regulated in two years time. So what have we gained? A system that still transacts benchmarked by the US$, but operated by private persons and creates an entirely new level of surveillance. Sounds like a great innovation.