Well, that was interesting.
With just a few hours to go, somebody placed a new bid of "up to $4567" on my camera, from a "compromised account" on eBay. This effectively locks out any last minute snipers, and would have left me high and dry when the auction closed.
eBay sent me a note that they thought the account was compomised, but didn't actually remove their high bid. Fortunately (I think), the system did allow me to manually remove the bid. Now hoping that the (previous, now current) high bidder hadn't given up and gone elsewhere..
Strange tactic, if that's what it was (?) (eBay neophyte here)