Mark Kolber wrote:
interesting. I thought I had an answer and then I checked. I deregistered a device in January but it still appears as a choice in Sync Devices
Which makes sense, because if your subscription is "full", you may need to de-register a device before you add a new one, but you may still want to capture the data from the old device onto the new one.
It may be that this question has not come up before. I don't think there's currently a way to delete devices from the sync menu.