You can also cancel and bid. If you see that a bidder has retractions in their history, you might want to cancel their bid. Two retractions would be enough for me to cancel their bid. Once you cancel a bid, be sure to add that person to your blocked bidders list.
Another reason to cancel a bid and block a bidder is if the bidder has a habit of leaving negative feedback. This may be a sign of a hard to please, unreasonable person whom you do not want to complete a transaction with.
Non paying buyers deserve unpaid item strikes.
