Yes you can un-authorise a device. Naturally for ease of use, it is an undocumented command...
For the PC I cannot say, but for the MAC, (from Adobe):
"...As you have stated that you want to
unauthorise the Adobe Digital
Edition on your Pc. I would request you to
follow the below mentioned
troubleshooting steps to de-authorize a
1.Launch Adobe Digital Edition.
2. Enter the unpublished key-combination of
Cmd-Shift-D (Mac OS X).
3.At the dialog, confirm that you wish to deactivate
4.Quit Digital Editions
To reactivate and authorize the machine using
the same or a new AdobeID,
just relaunch Digital Editions. You will be
prompted to activate."...
I would guess on the PC it is the CTRL key and shift D.
I just emailed Adobe support and they sent me the above. Quite why it isn't identified in the help or other commands I have no idea.
As for the Sony itself, I can't recall, but isn't it shown in the library software help files somewhere?