I've done a fair bit of business with Amazon and from what I've seen they are a very trustworthy vendor, esp if you buy direct from them. Fry's will even match Amazon direct pricing, so it's not like they are undercutting prices too low. Then again, they don't list Fry's as an authorized dealer either. Denon, Onkyo, Yamaha, Harmon Kardon and even MARANTZ!, all list Amazon as an authorized dealer. Onkyo, Yamaha and Harmon Kardon also authorize Fry's.
As far as I can tell, Pioneer is unfairly throttling Amazon (and by extension, Amazon customers), and Pioneer employees don't even know why. There's probably a lot of people buying Pioneer receivers off Amazon that aren't even aware they aren't going to get any warranty coverage from Pioneer.
So on the one hand, Pioneer offers some of the best, if not THE best sound at lower price points, yet is overly restrictive compared to other brands regarding where you can buy them from if you want a factory warranty. Seems just when I've narrowed down my choices, there's always something making me hesitate.
A little trivia on required signatures of deliveries. Newegg does not require a signature on any UPS delivered purchases, yet Pioneer sees them as a trusted dealer. There have been cases where people bought laptops costing over $1500 from Newegg and they were just left at the doorstep. At least Amazon requires a signature on any purchase over $1300.