The Dish Network announced at CES that they will allow off the shelf USB external hard drives to be plugged into their Model 622 HD DVR for 'off receiver' storage. This external hard drive will have a proprietary file system and will only be able to be transferred amongst the receivers in the house.
Events stored on the hard drive can be played from the hard drive or copied back to the receiver for playback. Should a hard drive get full, another hard drive can be connected for additional storage.