Just want to clarify here because the words you are using don't necessarily back your conclusion.

A person whose income is below certain levels is not required to file taxes.  That doesn't mean their income, from whatever source, isn't considered taxable income.  Did you intend to say that you don't need to report any Bitcoin-related income this year instead?

And related:
 - http://www.bankrate.com/finance/money-guides/turning-hobby-into-business-means-tax-breaks.aspx

[edited for clarity]