Well the important thing to keep in mind is that there are several ways to fund or de-fund a Mt Gox account. One method entails going to a local kiosk and submitting cash.
Sure, the feds can shut down all of them eventually but how many innocent people are they taking out with this Sledgehammer-Shotgun approach? This is reminiscent of their heavy-handed takedown of Megaupload which caused legitimate individuals and business to lose access to their legitimate date.