What I don`t understand is, if 1 bitcoin = 1 bitcoin, and in my bitcoin wallet all my coins are lumped together, how do I know how much capital gains I have made on a PORTION of those bitcoins? I don`t know which bitcoin is which or when/where I bought each one, it`s not like they`re physical objects I can easily distinguish between. Do we average all of our fiat-to-bitcoin conversions to determine the starting basis?

Hopefully the IRS will change things in the future when Bitcoin`s price is more stable.