Yes, but my point is, that still requires you to trust the counterparty not to tell others that you're connected to that key, which would allow them to follow its transactions. You can make it a little harder by having that account spend the money around to other accounts you're connected to, but it's still traceable.
It gets worse: Suppose a fraudster swindles someone else out of their money. The victim can go to the authorities with the fraudster's Bitcoin address. The authorities can force Mt. Gox to halt and flag any attempt to trade Bitcoins that, according to the transaction history, were once at the Bitcoin address that was used by the fraudster.
If the fraudster then spends his Bitcoins, and they eventually end up in your hands, and then you take the funds to Mt. Gox, you can end up getting charged with "receiving stolen property", even if the fraudster...
I haven't read/listened to them, but I thought these might be interesting to the local bitcoin users:
Eli Dourado (GMU econ PhD candidate) on the economics of cryptocurrency.
Econtalk podcast - Russ Roberts (GMU econ prof) with Gavin Andresen, Principal of the BitCoin Virtual Currency Project on, Virtual Currency.
Roberts' podcast is always stimulating even if I disagree with him, and Eli is a pretty insightful guy who I've met in meatspace.