A lot of retractions from other bidders?
Well, they could be innocent but scatty. Some bidders will bid on several similar items and then retract bids when they win one. Sellers hate those guys.
More likely is that they are working with the seller to raise prices. By retracting when the bid gets high enough they never have to pay and the seller gets a higher price. This is called 'shill bidding'.
Personally, I would not bid in such an auction or if it were something I really wanted, I would use a sniping service like esnipe to place a last second bid at my maximum. Late bidding, especially these computerized ones which literally can work in the last second of an auction, can be useful.
DH uses such a service because he competes in a small category where most of the material is offered on eBayAustralia. E-Sniping helps him win while he sleeps.