Brings me back to this topic, now we have even more dirty coins after the bter hack. We just have to accept it. Can't go on marking and identifying coins
Let me simplify the discussion for you because I think you and other want to jump into the macro way of thinking about this.
Lets say that today someone approaches you and says I have a great deal on 7,000 Bitcoins, I will sell them all to you for $100 right now.
Lets say you have the money to pay him.
Would you want to know if those 7000 coins were coming from the addresses that are part of the BTER heist before you made the purchase or not???
If you say you don't care, then I think you are not being a responsible member of society. You should care and you it is easy to check, so why not do it.