Though Amazon has its doubts about the concept, eBay (NASDAQ:EBAY) thinks its can provide same-day delivery on a large scale. "No one single retailer can do it on their own, so we are building it for the retail industry," says CEO John Donahoe (previous) at a Goldman conference; he envisions offering retailers a bidding platform for unused delivery inventory, and thinks there's more than enough to go around. eBay is trailing same-day services in NYC and San Francisco, and is also experimenting with home pickup.