Whether or not you intended to earn a profit only matters for tax purposes if you didn't make a profit. If you do make a profit, it matters not one bit whether it was accidental or by design.
The reason I specified "here" (Australia) in my post is because different laws apply in different jurisdictions. Not all profit is regarded as taxable income here. The most well known example of that is us not usually having to pay tax on gambling wins or on income generated from hobbies.
Intention also matters here when the Tax Office is determining whether an activity is a hobby or a business. If it's a hobby, the income and profit aren't taxable but nor can you claim deductions or losses.
Do you have the purpose of profit as well as the prospect of profit? Do you intend to make a profit or genuinely believe that you will make a profit, even if you are unlikely to do so in the short term?
http://www.ato.gov.au/corporate/content.aspx?doc=/content/00199712.htmIt's a good time for this topic to come up as it's tax time in Australia right now and people need to make choices about whether or not they're going to declare Bitcoin income and if so as what type of income.