While I agree with you that the Silk Road is a good thing I don't think blocking those coins will do anything for anyone. The FBI will get the money they need to continue their crap whether they get it from selling bitcoins or from the money printers.

Plus, singling out coins and designating them "bad" is a very unsavory president to set. What happens when the coins someone want to mark isn't such a bad thing? Let's keep freedom free and be a good example, not play their game of attempted control.