This. Blacklisting stuff I might buy then find I cant spent unless I trick the next person.

Interchangeability is fungibilty, serial numbers don't stop 10$ notes being interchangeable. But if a set of serial numbers were invalidated somehow then it could be an argument.

The British Bankers’ Association Money Laundering Advisory Panel (the “BBA Panel”) raised with the Home Office their view that the requirements of the consent regime in this context cannot easily be reconciled with POCA’s wide definition of criminal property and the principle of fungibility. The BBA Panel explained their view that money in a bank account is fungible
and that as a matter of property law a bank account is a single “indistinguishable mixed fund”. Consequently, once a payment has been made into a mixed bank account, that payment cannot be distinguished from the other funds in the account and, accordingly, if the payment was a suspicious transaction the payment funds could have effectively tainted the rest of the account and, possibly, any other account held by the same individual. This would result in all subsequent transactions on the suspect accounts becoming acts of money laundering under POCA.