If I had more time on my hands: (1) Launch a Bitcoin capital gains/losses tax approximation application (the "App") in beta. User keys in their Bitcoin addresses. App searches the block chain for the user's entry and exit times. App searches exchanges for the most favourable pricing source. App then returns an approximation of taxes owed/to be credited (e.g. in case of coins lost at Mt. Gox). App has a prominent disc…
The taxpayer has to be consistent with how they determine the price of bitcoins, generally meaning that they have to use the same method unless they have a good reason for switching. Deliberately choosing the most favorable pricing source is fine the first year--but they'd have to stick with the same source in subsequent years.
Also, the app would be enabling tax fraud. A "prominent disclaimer" isn't going to be much protection. If anything, it's likely to be used against the appmaker to demonstrate willful blindness.