> I am aware many exchanges/markets do 'bitcoin mixing' to get around this, but the local authority could just as easily subpoena/force someone like mtgox into giving up the info of where the coins are going.
The coins are mixed _before_ they arrive to mtgox or some exchange, I would guess.
> Even if you mix the coins a few times through a few sites, its still going to be the best way to find them.
Any arguments here? The authorities would need information from every web site that has been involved with the transfer. The mixers can reside in the tor network, so it is impossible to get the connecting information.