Well, as with any OS if you mess up certain files you can render it unbootable. It's very hard to really brick the nook tho, because you can physically access the System SD card.
@ctos -- follow the nookdevs guide on the nook disassembly and get to the system SD card (will void warranty tho). Alternative way would be to create a custom "update" image to remove the wpa_supplicant.conf file.
PS. Oh, you might also try this way of multiple resets, it might delete the wpa_supplicant.conf file as well.
Last edited by stangri; 02-25-2010 at 01:20 PM.