[gruez]

You can't say "don't touch coins from these addresses" because it would be trivial to DoS people by sending dust from a blacklisted address to other people's wallets.

[acdha]

If they sent more than infinitesimal amounts, it’s unsustainable; if they don’t, it’s easily filtered — and that’s assuming that they didn’t just direct you to send the amount to some dump address if you wanted to disavow it. Simply telling a few large exchanges to do that automatically would take care of the majority of users.

[throw99c]

You have to be loaded to consider DoSing with current transaction fees anywhere near practical.

And it's not like the government couldn't fine the businesses equal to say, 1.5x the amount transferred from the blacklisted address.