I've sold a 30GH unit about 2 months ago on eBay went fine. Of course those go for double the price I sold it for now so I don't think that guy was going to charge back
bobsag3 sold twenty or so singles on eBay, of which two he reported had chargeback issues. So about a 10% chance of eBay problems I think. I sold 160GH of Avalons last month and contacted the buyer directly to make sure it all seemed on up and up. So far so good, but I will still wait 30 days from delivery date to make sure.