Although it blows that mtgox and britcoin seem so reticent to give help to government agencies instead of just complying with them when they ask for information, this is not unexpected.
It is a good news indeed.
Now decentralized blackmarket exchanges will emerge, protected by TOR and other anonymous networks.
And having legal exchanges like Mt Gox and Britcoin is also very important. I expect it to work like this:
Blackmarket goods <-> Blackmarket exchanges <-> Cash <-> Legal exchanges <-> Legal goods
This.