I buy new (or factory refurbished) stuff on eBay all the time. Not Kindles, but then I don't buy Kindles anywhere else either...
Why? The three main reasons: Non-US credit card payment (PayPal), international shipping options and availability of factory refurbs..
I do however do lots of price research and I'm often amazed at the prices US buyers pay for things they can easily get online elsewhere. Someone mentioned auction frenzy and I'm sure that's true because I often see auctions ending up above buy-it-now prices from other sellers.