Given the old saying about how the simplest explanation tends to be the correct one, here goes:
He bought it used and never bothered to even change the system name, etc. I sold a SP 1.6 G5 to someone just one month after I bought it when I discovered a cheap way to get a DP 1.8 for just $200 more than the guy was willing to pay me through the want ad (I sweetened the deal with MS Office). Not only did the guy who bought it from me not change the name, he STILL USES MY OLD PASSWORD, MY DECEASED CAT'S NAME! I happen to know this because he stills calls me up from time to time when he installs new software because he can't remember the password.
The point of the above info is that some people really are just as stupid as the simplest explanations require them to be. Most people who break into homes and have the musculature to haul off with a power mac G5 tend to hawk them on the street or in a pawnshop ASAP - not patiently it through advertising.