I bought a pile of crap ebooks from info-books that were out of date and most had broken links. When I left negitive feedback, he offered me £5 to retract feedback. Sure I could have made a small profit from doing so, but I said no and reported it to EBay. Ha, he is still ripping people off today, 1 year after I complained about him. I sent ebay all the proof of a SCAM and the BRIBES, and they did nothing.
As for Paypal, if a buyer buys an item and don't like it, he can complain to Paypal saying item faulty and get his money back, less postage for returning item, even when the item is not faulty. Trust me, this happened to me.
So, before everyone thinks Sellers are all out to rip buyers off just concider the time wasting buyers that do not read the adverts correctly, causing the sellers to suffer.
Last point. I have been left positive feedback on all my items. On occation I have been unable to leave others feedback because of EBays faulty software, costing me about 20 positive scores!