There are legitimate and illegitimate reasons for a seller to choose the Private Listing option. (You should be aware that YOUR bid on that item is/would be attributed to the same "Private listing--bidders' identities protected"--note the plural; you see your own ID in the bid list only because YOU are the one logged in under that ID). Private listings protect the winner's/buyer's (they apply in fixed price listings also) ID to a greater extent than in ordinary listings (a***b type alias; though the legitimate differences are getting fewer and fewer as eBay is getting more and more opaque with ordinary listings), by keeping the item off an Advanced Search by Bidder (no longer available on ebay.com, but possibly still available to application developers) and not displaying the item title and # in feedback (but the latter is no longer done on the buyer's feedback profile, and the buyer's ID is now anonymized on the seller's feedback profile, but it is still possible, with some effort, to match a feedback left from a buyer's profile with its appearance on the seller's profile to find the item information). Legitimate reasons include the sale of items where the buyer would most likely want his/her identity kept private (adult materials, medical supplies, spygear, etc.) and that the likely buyers of the item are a small tight community (small and tight enough to know each others' ID aliases) where one might be reluctant to bid against another. You guessed at the main illegitimate reason (the term is "shilling").
My rule of thumb is that if the majority of sellers of the item or very similar ones use Private Listings (especially if they use it for their fixed price sales) then the reason is probably legitimate. If not, I go with one of the majority of sellers who don't use it. Or I might discount my bid so that there isn't enough room to run it up past where I would be very happy paying. (It could be that the seller has a legitimate, or at least non-illegitimate, reason for choosing PL, that the others don't, in which case I might get a bargain if my higher paying competition is scared off.) AND the best way to avoid having the price you pay if you win be higher than it should be because of shilling is to wait until the last minute to bid your TRUE maximum without regard to what others have bid or don't appear to have bid; if you don't let YOUR bid be affected by shill bids and you don't give the potential shiller time to probe YOUR bid, the price you pay will be based on a legitimate valuation independent of your valuation: either the maximum bid of the next highest legitimate bidder or the true minimum selling price of the seller, within an increment or so.
Note: if there isn't already a bid by someone else on the item, the only way to tell it is a PL is to look WAAAAAAAY down on the item's Listing Page (past the point where you'd think there would be any information about this particular listing) for something like this:
"This is a private listing and your identity will not be disclosed to anyone except the seller."
lady_madonna
