as far as i know, you need 3 NPB complaints against you before ebay will ban you, i believe it goes warning email, second warning- threat of suspension, and then permanent pan.
Unfortunately, the only way you can get feedback retracted is by using squaretrade paid service for mediation and then they can retract the feedback.
I have had problems with NPBs in the past, but what i find is that i ask in my auctions that if you feedback of less than 3 or have joined in the last 30 days then you email me with a contact phone number or email address to verify your identity. This will put off most time wasters, if someone does bid, i email them, and then give them 24hours to reply, and if i don't hear back i will cancel the bid to save myself hassle.
Bid retractions can be complained about to ebay if they do not give a good reason, but again the user will just get a warning about this.
You can set up an auction that is only available to pre-approved bidders, and then everyone has to contact you before bidding but this can result in some people being put off and therefore you getting a lower final price. You can also ban certain users from bidding on any of your auctions, so if you have one person bidding on loads of your stuff ( i had a guy who bid for 5 of my items then claimed he didn't understand how paypal worked and couldn't be bothered to send a cheque. despite this he kept trying to buy from me so he was stopped from bidding on my stuff) but this only really helps if it is one person bidding over and over.
hth
MB
