the limit should be unlimited. if someone has already pay taxes on money they put into bitcoin, why should they have to pay taxes on it again? eventually the government wins and gets everything.
I do agree. As nullama has pointed out, with bitcoin you are paying capital gains tax on your profits as measured in USD, at least in the US anyway. And you can claim tax relief on your losses. But all that hinges on the fact the IRS treats bitcoin as an asset. It would be far better to treat bitcoin as what it is - a currency - at which point these taxes don't apply.
We will have much more success in excluding small value transactions from these ridiculous tax laws in the first instance than trying to exclude all transactions.