Another thought. Most of these coins would have been mined in 2012. The IRS just released guidance for the first time a month or so ago. Am I really supposed to go back and report these mined coins?
Yes. However, if they were mined back then, it might not be all that much income, so you shouldn't have a
huge penalty.
And either way, what is my cost basis for these coins? Ahhh!!!
Figure it out to the best of your ability. Guess if you have to. Then, claim those bitcoins as income at that point based on the btc-e exchange rate at the time (since that is the primary exchange you use). As far as how you declare them for capital gains/losses, however, you need to be able to prove that you owned those bitcoins at that specific point in time. So for that, the date bought would be the earliest that you can prove possession, but with the basis you got when you calculated how much income was generated.