Most docks are little more than a plug with some extra plastic, but the Nexus One dock, recently leaked by the FCC, has a bit more.
Bluetooth, in particular, is a notable addition in the dock (since Bluetooth is already in the phone). In other words, you're docking a Bluetooth device into another Bluetooth device. Why could this be?
Really, there are many explanations—and Bluetooth is cheap enough at this point that it need not be a luxury. Maybe HTC wanted you to have a headset that you kept at home. Maybe Bluetooth was chosen for remote accessories. Maybe Bluetooth just sounds cool to engineers.
Regardless, the thing'll have Bluetooth. Oh, and from the looks of it, the dock will hook into your home theater as well. [FCC via AndroidForums via Engadget]