Going a step further, from where CyberPet left off, I would say that having a large number of positive feedback is only helpful (in Apple laptop auctions, where fake ones are more than legit ones) if the feedback is referring to auctions where this guy was a Seller and was selling similar stuff. I have seen many Sellers with a very high positive feedback, BUT they were either buyers or they were selling Star Trek model dolls for $5.99, which is quite far from selling $2000+ items. Some of them go the extra step and set up fake auctions with their buddies, they end them normally and get positive feedback from them even though no transaction actually took place.
Fake auctions on Powerbooks is of epidemic proportions on ebay, especially after the new machines were announced. People are leaving (fake) positive feedback on pre-sale auctions from machines that they could not possibly have received (like th 17" G4).
On high ticket items like these, especially since Powerbooks seem to be the crooks' favorites, one should do the following:
1. Check the feedback carefully and see if the Seller has received positive feedback on the sale of similar (and similarly priced) items.
2. Ask to pay either COD or using escrow and offer to pay the escrow fees, or arrange for a personal pickup and money exchange if convenient. There is no reason for a legitimate Seller to say no to any of these options, as they provide the highest degree of security for everyone.
I have been burned before (with a Nokia 9210 Communicator auction) but luckily I was able to recover my money, so I am extra careful now. Hope this helped:)