I've been thinking of trying to pick a notebook up of of C/L myself as well. I've been amazed by both the high and the low prices I see there.
Some guy seems to like to buy unit, load every imaginable piece of software on them, then sell at a big markup. Other people are strangely enough selling units that don't have any accessories, including the power cord. Makes me wonder how they came to possess these...
Anyway, what good would knowing the serial number be? Is there a phone number where those reported as stolen are logged or something?
I find it hard to believe that people are selling a lot of G4 ibooks and powerbooks for 600-700 bucks. Why would anyone pay that over about 1000 for a refurb C2D macbook? I would like to get a 12" powerbook G4, but I don't expect to pay over $500, given what is available now.