The only concrete example I could find is https://www.nbcnews.com/id/wbna26959902 https://www.nbcnews.com/id/wbna26959902 (though to be fair my research here co

The only concrete example I could find is https://www.nbcnews.com/id/wbna26959902 https://www.nbcnews.com/id/wbna26959902 (though to be fair my research here consisted of checking the references on the Wikipedia page for "Marked Bills"). The important thing to remember here is that possession of stolen goods or cash is a crime (cf for example https://www.law.cornell.edu/uscode/text/18/2315 https://www.law.cornell.edu/uscode/text/18/2315), so if it becomes known to you that stolen cash is in your possession, you have a legal obligation to give it back. Given how fungible cash is, this probably won't be enforced if somebody uses stolen cash to pay their bill in a restaurant, but it probably would be if someone bought a car with cash that could be traced directly back to a bank robbery. Since bitcoin is infinitely more traceable than cash, the argument of "but how do you know this particular dollar bill was stolen?" wouldn't really be applicable.