Truly, Bitcoin aids money laundery especially in developing countries. Bitcoin transaction is kept on blockchain which allowed people to traced it, the transactions are never truly anonymous. Many illegal activities going through bitcoin but the evidence still there, including money laundering. However, my concern about sites offering to mixer bitcoin, so it can't be traced right? But, I don't think those mixer sites will easily accept money laundering. That's why some countries issued regulations about bitcoin and exchanges to prevent any kind of those transaction.
What do you mean by that? It's not the purpose of mixing sites to ask for the origin of funds. M'm pretty sure that with enough effort the mixing algo could be reverse engineered, so no action that you take is untraceable. It's just that you would have to be a first class criminal for them to want to get to you this badly. They would have to invest a lot of money and time to trace coins after they've been mixed and that's why it gives additional safety and anonymity to average users like us, but I wouldn't use a mixer to hide a couple million dollar drug deal. I wouldn't choose bitcoin for that at all.
Though bitcoin is a anonymous transaction but because it is digitally transaction, there's no way it isn't traceable because there a program that can trace the origin of your transaction if your identified scammers or launder. Because of cryptocurrency currency criminality would be lessened.