People visiting Amazon.com intending to buy various items:
a) want the shipment and customer care to be handled by Amazon. (Since they have showed that they area really good at that kind of thing)
b) want to have the goods vetted for basic safety etc etc.
Basically, Amazon needs to rewind/rebrand/remove its second-supplier Bazaar style listings from its main index.
Maybe the could display a two column search result page? Most people have wide screens now. Amazon-handled to the left, rest of the world to the right.