I can't imagine tax authorities asking you for your Bitcointalk login or private keys. They certainly shouldn't, and technically that wouldn't prove ownership of the funds at the time they were paid. I'd archive the sig campaign threads in case the site gets nuked, but that's more about proving where funds are derived from and less about taxes.
I think the IRS really just cares that people are making a good faith effort to pay their taxes. It seems like signature campaigns would fall under regular "wages/salaries/tips" or "other income" and taxed at the standard tax rate for the cost basis, and capital gains for any gains from holding.
They won't really care. None of them care. You just tell them you have a screenshots and few bits and bobs that'll let them offload the problem on someone else if it ever arises, and it won't. They won't even ask to see them.
This also even a risk to some 3rd world countries. Unlike those countries where bitcoin can be freely used. I guess this is the downside of taxless transactions. Some government banned bitcoin they though it will just bring their country into a bad demise. Also government cant really profit if that is the case. Some may say that bitcoin is some kind of tax evation but i think the only problem is dictating where you get your profit.
When citizens already come to a point that they are not paying taxes and decide to hide up assets on bitcoin form then it will surely put up the entire country into problem since we do know that tax do really play major role on the economy of a country and if people do not tend to pay up their obligations then it would really give negative effects.
i was only today talking to a friend about this.
Going forward how do we liquidate crypto to fiat ?(unfortunately it doesnt look like we can use crypto widely)
i am in europe and i know if there is any deposit made greater than 5000 questions will be asked and potentially subject to tax.
Each country do have different limitations when it comes to max transactions which is normal because they do really need to impose laws that would really fight money laundering and tax evasions and other related cases.