In November of 2011 Mt. Gox demonstrated control of 500k BTC. I followed the 500,000 BTC for a bit beginning at https://blockchain.info/tx/b269bf1b82dae8a61f7f91dbf7a9d807e... . The coins move around and small amounts are sent away, but the majority ends up back in Mt. Gox's main (hot) wallet. This repeats a few times until the majority is paid back to the main Mt.Gox address. Here is the transaction where it starts…
I'm a bit new to bitcoins, but is it technically possible for the bitcoins community as a whole to make a blacklist of bitcoins addresses and "ban" the stolen bitcoins ? Such blacklist would daunt robbers and enforce public trust in bitcoins.
The problem is that who then decides which coins are "bad"? Does the US Government get to decide? How about coins that fund organizations that the US Government doesn't care for?
My personal opinion is that no bitcoin should ever be tagged as better or worse than any other one. By messing with the fungibility of the currency, we would do way more harm in the long run than good.