eBay.ca has also changed to 'Bidder 1, Bidder 2'. The explanation for the change is similar, but the differences are interesting.
"As the internet evolves, eBay continues to strike a balance between preserving transparency and protecting our Community of members. eBay has decided to change how bid history information is displayed so bad guys cannot target bidders with fake offers using this information. In certain cases, some bidders will no longer be able to view Bidder User IDs on the Bid History page. Your User ID will be shown only to you and the seller of the item you're bidding on. Other members will see an anonymous name, such as Bidder 1, applied consistently to the Bid History page."