Among the main problems on eBay is the lack of anonymity. Bidders have the perfect right to privacy in auction sales. Some individuals want to be known at auctions-largely for egotistical reasons or to establish a name as players in a certain market-that's their privilege, but anyone seeking anonymity should be able to preserve it. I believe this is now possible on eBay but I'm not sure.
The other practices alluded to of syndicate bidding, etc. are governed by commercial law in most states. Since eBay is international, I don't know what law pertains.
Syndicate bidding, in which several people pool resources to buy at auction, can lead to higher sales prices, since if someone alone is willing to pay $1000 for an item, three can easily pay $3000 for the same piece leading to greater profit for the seller. It's most frequently done to bid higher rather than lower. Sometimes two individuals can arrange to get out of each other's way in a sale with multiple similar lots, but there's little honor among thieves.
As far as the danger of bidding against friends, other dealers, etc. that's easily remedied by an eMail or phone call. I've found that friendship evaporates when a rare item appears at an auction.
In any event, eBay's biggest problem is at least making an effort to control known rogue sellers.
They may be forced to soon.
George Hollenberg MD
CT, USA