When the bidding list shows Private Bidder it means the seller has set the auction up as Private....often done for sensitive items and higher priced collectibles.
The item title and price paid does not show up in feedback, making it Private.
The reason you can see your ID but everyone else is Private is because you are logged in to ebay....log out and look at the listing again and you will see what everyone else sees...Private bidder. Only the seller can see the full IDs of all the bidders, and you can see yours.
This question has been answered a number of times....if you scroll down the page you will see some of the other threads.
