Gene asks a good question: "Maybe I'm stupid, BUT, Why would you want to hold an auction on a service, that everybody can not get to?"
A simple answer: when I started live cyberauctions on Prodigy about 6 or 7 years ago, there WAS no Internet - at least not that we common folks could get to. Proprietary online services (Prodigy, CompuServe, AOL, Delphi and a couple of others)were the only means of cybercommunication at the time. I believe it was the first attempt anyone had made to conduct a live online auction, with people from the entire country able to bid real-time for chips.
Prodigy auctions continue because there's a core of 70 or so chip collectors who are still active there, and about 20 who regularly participate.
Interesting, though, that I've posted the lot listings for the last couple of full-blown auctions right here, and invited e-mail bids so that "everyone" can participate. Didn't receive a single response.