Impossible. You'd have to somehow convince ALL miners to not process them.

Fungibility prevents you from simply blacklisting these coins.

http://themonetaryfuture.blogspot.it/2013/12/why-bitcoin-fun...

Actually you just need to update the code and push it via the update mechanism.

Code of what? Bitcoin is not one central code base with a global update system.

I have little sympathy for Mark. Assuming he didn't straight up stole the money, it all happened because of his incompetence.

How do you not notice a leak of 850,000 BTC?

How do you not have most of it in cold storage?

How do you not have all kinds of alert systems warning you about even a 500 BTC discrepancy, let alone hundreds of thousands?

You have to get bookkeeping exactly right.

You have to get crypto exactly right.

Bitcoin sits on top of both of those sharp pyramids.

Yesterday someone on HackerNews compared a Bitcoin account to a pressurized system where the slightest failure means you lose everything irretrievably and instantly which is a great analogy.

You don't need Good Enough for this. You need Perfect for this.

No you don't need perfection to add some basic controls that would have prevented most of the damage here.

Hence the theory that the missing BTC is in cold storage but the private keys have been lost.