If you're an eBay seller or buyer this is a must! As a buyer it's obvious, you want to know if the seller ships items after payment, if the items are in described condition, etc. Usually feedback is comprehensive for sellers but as a seller on eBay, I've become aware of how it's important to screen out buyers.

On PurseForum, there have been incidences listed of reverse scams on eBay. I.E., you sell a Chanel bag for $2000 to some buyer. After receiving it, buyer claims it's fake and Paypal/eBay sides with them (if for some reason you can't provide proof of it's authenticity even though it is) and you're forced to refund them. They send back a fake bag: you're out the bag AND money. Other issues include malicious buyers who for some reason leave negative feedback on a rampage or has a history of scamming sellers via different usernames that eBay does not regulate or try to put a stop to.

Toolhaus lets you look up a username's negative feedback, including buyers' that eBay has made invisible now on the main site. This helps you judge on whether or not you're dealing with a fake bag scammer or a malicious buyer.