So I've a question about situations like this. I believe that a chain of transfers can be created with bitcoin. So couldn't a blacklist be created? That would allow users to ignore illegally obtained coins?
This also removes features of bitcoin that some view as advantages, namely that there are no chargebacks and no-one can forcibly remove your funds. In bitcoin, once you have it, no-one can take it from you (unlike, say, paypal). This has disadvantages if you're the victim of a theft. Bitcoin is also a decentralised system, so you'd have to convince everyone that you are the victim of a theft, and that these transactions are to be rolled back. Other wise someone could pay for a service in bitcoins, then try to get everyone to roll back the transaction, and hence deprive someone of the bitoins.