[icebraining]

2. If the government wants to ban certain activities it can do so easily. Suppose that the government wants to keep its citizens from gambling or from using mixer services, it could declare that it won't recognize Bitcoins that passed through those services as legal tender. Good luck paying property taxes with your tainted bitcoins.

Bitcoins aren't actual "things", they're just values that get debited from an account and credited in another, so you can't have tainted bitcoins.

You could have tainted addresses, by checking if there's a path between a certain address and the blacklisted ones, but then anyone could taint anyone else's address by just sending them a Satoshi.