Yes, there's already the Zerocoin proposal... which will require big buy-in from existing stakeholders to get grafted into the protocol. What if big Bitcoin op

Yes, there's already the Zerocoin proposal... which will require big buy-in from existing stakeholders to get grafted into the protocol. What if big Bitcoin operators get a message from the tax-and-law authorities that they welcome Bitcoin just the way it is, thank you very much, but will start to use the levers at their disposal if large remixers or Zerocoin-like extensions are added? Or what if the authorities just say, Bitcoins that have never been Zerocoined are great, but those that have been through the Zerocoin-blinding are contraband, and can only be cleaned by declaration and payment of a significant punitive excise tax? The nature of Bitcoin and the Zerocoin proposal leaves completely transparent which coins are 'tainted' by participation in a previous verboten transaction.