Rubbish. I am far from a bitcoin cheerleader, but i can't imagine that this is the government firing an opening salvo at bitcoin.
Why would they cut off only Dwolla, but leave Mt.Gox standing? US clients can still wire funds to and from Gox, and can transfer their bitcoin balances anywhere they choose.
Why wouldn't they call in a favor from Japan and raid Mt.Gox's offices there and shutdown their computers - that would freeze all of the money that Gox is holding AND freeze all of their clients Bitcoin balances? Think about what the gov't did to Kim Dotcom and attempts with the Pirate Bay.
Why would the lead be taken by the DHS rather than the Treasury or Office of Controlled Foreign Assets?
Why would they leave the mt.gox domain name operating as normal? They pull domains that are linked to illegal activity at the snap of a finger, why leave Mt.Gox up and running?
And why go after Mt.Gox first - I mean, yes, they're the biggest, but with a few swieps of the pen, the government could shutdown every bitcoin exchange and transmitter in the US. It would take just about no effort to accomplish that, and then they could focus on the big fish.
And would they really need to go through that effort? they've got the NSA - i'm certain that those fellows could direct enough resources at the bitcoin network that they could overtake the collective hashing power that the network now has. Maybe not immediately, but in a relatively short period of time. All they would have to do is broadcast they they now have the majority of the hashing power, and there goes all confidence in Bitcoin. Who would tie up any capital in there at all if they know that any single entity could suddenly decide to start overwriting transactions and generally causing all sorts of havoc to the network?
So no. As much as I don't think bitcoins have a long-term future, or even a medium term one, this isn't an opening shot of a bigger war.