>Are the people buying these radios off Ebay simply trying every possible code >until they get the right one?

I thought 3 or 4 wrong entries shuts the radio down for a while
(you leave the key in accessory for 30 minutes or so to clear it).
So that would make random checks hard.

I wonder if you could report a stolen radio to Volvo or at least the
code. This way, if someone asks for the code and it matches
the radio would be found? I worked at a Unix workstation vendor for a
while and they would do this for stolen computers (so when a service call
or help desk call came in for a system the serial number was always
checked against known stolen systems).