I am an accountant in the United States currently studying for the CPA exam.  Here is my take on the taxing of bitcoin and what I have learned from talking with some counterparts.

Technically...you owe tax on bitcoins if your a merchant or you realize capital gains.  For anyone selling items this is easy.  In a nutshell(yes obviously there are deductions and credits and what not) you owe tax on whatever was brought in minus what it cost you to produce the item.  AKA revenue - COGS.

Mining bitcoin is where this gets tricky.  Let me preface this by saying that no official word has been given from any government entity on how to handle cryptocurrency gains.  There have been independent companies that occasionly realease statements that pretty much amount to that "soon" (probably soon as in BFL soon) bitcoin will have to be looked at by the government.  Most of those 3rd party reports admit to no official ruling out, but that you probably need a license (I forget which one, I think it has to do with trading) in order to do any merchanting that involves bitcoin.

Obviously, that was a tangent that had hardly anything to do with taxability of mining earnings.  We have learned that there is no official ruling as of yet, but, the U.S. Tax Code is very vague for reasons just like this.  The main point to remember with U.S. tax is that there is no definition of the word "income" anywhere in the tax code, and no government agency will ever release a definition, and this is for good reason.  This allows them to basically set and change rules whenever they deem fit and cast a pretty wide net on what is taxable.

So, the generation of bitcoins are taxable, but, what/when should they be taxed.  Since we dont have an official ruling, we do not know if they are a security (investment) or a currency.  If a currency, you would owe tax when they are generated, but if a security, then you would be taxed at the capital gains rate when they are realized (IE converted to cash). 

This brings up more questions though, what basis should be used for the coins, can we deduct the expenses that were used to produce them?  Should the cost of your mining equipment be depreciated over a 5 year life cycle and is the electricity costs associaited with producing coins allowed to be deducted?  If we need to realize the value of it when it is created, how do we do this with an ever changing value of the currency.  Just because it was created yesterday and then the price took a 30% dip today, does this mean I should be taxed at the higher price when it was created?

As you can see, there are many questions that need to be answered.  My best advice as of this time, and I can in no way be held liable for giving this advice and any action on your part is completely of your own free will, is that you should pay tax on them when they are realized.  IE buying somethng or converting to cash.  They should be taxed at capital gains rates, and you should be able to deduct the expenses you put into it (if it is a dedicated rig, if your rig is also your personal computer or gaming computer or anything other than bitcoin, you cannot deduct its cost)

Of course, if the coins are used to buy gold or silver, which are not comoodities or stocks, then this complicates things further.  What basis do we use now?  My thoughts on this would be that the basis rolls over and you will still have to recognize gains on the liquidation of the gold or silver.

My thought is though, what if you buy gold or silver and then put it into an RIA?  These grow nontaxable, and lead me to believe that by doing this you can grow your investment tax free and then only have to recognize the gains when you start drawing from it.  This is just a thought that I had, not sure if it is possible or not or how it would be viewed.

I would say that you shoudl just go for whatever you want though.  With something new like this the IRS will probably just slap you on the wrist and worst case scenario make you pay back taxes which you would owe anyway, without any interest or penalty.  Again, YOU SHOULD PAY TAX!  I in no way endorse this strategy, it is simply what would probably happen based on past circumstances.  It is also a possibility that they will make an example out of you (probably if the amount is big enough) and tax you out of your freaking mind.  So that is a judgement call based on risk assessment.

Let me repeat, these are my own opinions based on what I have been able to gather and what is provided in past ruling and the tax code.  They should be viewed as such and nothing that I saw is legally binding or should be used in conjuncture with any IRS rulings.