Ok, re-reading it more calmly Mike isn't proposing it or taking any stance he's looking for ideas on any aspect of it. It already exists, it can be done using the just the blockchain so I'd guess discussion should be as much about possible ways of preventing tracking as about ways of implementing it. That works both ways, making it hard for a government to track coins and extort 50% of your holdings also makes it hard to track the those extorting coins out of the little old granny with cryptolocker. That makes it a lot bigger issue than it seems, tracking can already be done but for now its restricted to specialists.
The problem is that the government could be behind both of these instances. A government can create cryptolocker ransomware technologies and spread it viral to tax the entire Bitcoin community by preying on the weakest members. It will be something governments could sponsor and use to steal money and I would not be surprised if a government were behind cryptolocker.
So it's a very serious problem which I think people on this forum are underestimating. Cryptolocker could destroy Bitcoin just like the blacklist can.