Colin Rule was director of Online Dispute Resolution for eBay and PayPal from 2003 to 2011 and was recently interviewed by Auctionbytes (see here).  He came up with some good insights.

On duration of a dispute and using it to change a otherwise often bland buyer/seller relationship he says "We discovered buyers would rather lose a dispute quickly, say within a week, than win a dispute and have it take a month. The added headache of worrying about the matter is more painful to them than the injustice over losing $50-$75. Second, disputes are an incredible loyalty opportunity. We compared hundreds of thousands of user accounts and discovered that users who filed disputes used PayPal more after the dispute than users who never filed a dispute in the first place. And that was regardless of outcome - even users who lost their dispute were more loyal. Why is that? It's because users who never have a problem barely register who they bought the item from, but users who do have a problem definitely focus on who sold it to them and how the resolution experience went. So in many respects, transaction problems are major opportunities for merchants."

And on eBay's decision to stop sellers from giving feedback he opines "From my personal perspective, I think it was a bad move. I know all the reasons why they did it - no other site on the Internet, or store in the U.S. even, rates buyers on their performance. Buyers would get retaliatory negs and they were gone. The feedback team knew they needed to solve that problem, so they made the change. But for me, the bi-directional nature of eBay was what makes eBay so special. Community requires interdependence. It's not just the buyer is always right - that works short-term, but it weakens the ties long-term. eBay always blurred the lines between seller and buyer, and the feedback system was part of that. Once the accountability only went one way, a big part of what incented buyers to be reasonable went away, and with it some of the interdependence was gone."

We agree on both of these and hence have automatic rules to solve more than 99% of the disputes that we expect on our marketplace and mutual feedback!