Attempted government regulation of Bitcoin was inevitable, I suppose, and would make sense if you didn’t know much about Bitcoin. Dirty money can certainly be sent into it. However, it is difficult and slow to get Bitcoins out and exchanged for old school money. Adam Curry mentioned this recently on a No Agenda podcast. They wanted to take contributions in Bitcoin but found the maximum amount most anyone would cash out at once is 2 coins or about $90, which pretty much makes it useless for contributions – or for money laundering.
My view: the government and their fellow traveler corrupt banks don’t want any upstarts competing for laundering money.
The only thing holding up the US dollar is its primacy in valuing other currencies – in essence, its importance to other governments. If an independent currency got widespread traction, our currency might fall to the levels of its actual inflated value.