The courts are full of people who believed that they are somehow exempt from taxes. In the U.S. there is no such thing. As Burt mentioned above you owe taxes no matter how you got the money. It may have been a big gift, you may have found a gold ring on the beach, or maybe you mined a gold nugget. It does not matter, you owe tax on it.
What is sad is how many bitcoin users have deluded themselves into thinking they can't be caught. They are going to profit big from the best economic opportunity they have, then loose it all to the IRS and wind up in jail because they wanted to evade taxes. Why do that when all you have to pay is capitol gains on your profits?
I know for a fact that the tools to find bitcoin users have been under development for a while now. Every Tx you have ever done is on the blockchain and a few years from now the IRS is going to come for the money you owe. And they don't accept excuses.
I disagree with the idea that using bitcoin would probably lead to a tax evasion charge, consider this:
Has normal use of bitcoin ever led to a tax evasion charge?
I do not expect that IRS will open this can of worms, it is more reasonable to expect the status quo to continue; despite the fact that very few tax returns mention bitcoin, normal users have not seen tax evasion charges at all!
I predict that you will eat your words in a few years. For the average user there is no need to disclose anything about bitcoin to the IRS, and IRS does not have the resources to pursue an average user.
I never have filed taxes on anything because I will not be voluntarily paying that protection money as a matter of principle, the principle of economic freedom! In the USA there were supposed to be NO debtor's prisons and unlimited right to contract, also no search and seizure without a plausible link to a crime of harm. Corporations get away with tax evasion by way of their transfer pricing practices, yet you want bitcoin users to pay taxes because you are in fear of a tax evasion charge.