I assume users were receiving bitcoins that were mixed and more likely some users would end up with bitcoins that were used for black market and other illegal activities.
I have euros, dollars and pound sterling that have most likely at some point been used criminals. Simple evidence:
most bank notes contain traces of cocaine, and there are countless other crimes that don't leave physical evidence on the money.
None of this is a problem for me, because money is fungible. And no government would dare take that away, because if they do, it will be the end of money as we know it.
Just imagine you can't accept money without checking known and unknown crimes committed by all previous owners.We all know that but that's never how it works. Criminals can and do easily use their dodgy black-market money on the high street and supermarkets etc but those places would never be prosecuted for money laundering or handling illicit money etc but you as an individual could be if they deem you are handling or interacting with illicit cash. It's sadly just how things work. I always find it funny how people cry that bitcoin is a tool for scammers and drug dealers but 99% of scammers just us bitcoin as a medium to sell for cash and most drug dealers don't accept bitcoin. They only accept cash because it's pretty much untraceable, is very easy to launder and there's no record of it kept, but nobody seems to be making that case right now. I'm sure they will do once they decide to go to a 'digital dollar' so they can keep an eye on everybody's transactions and tax is appropriately.