Half of my Amazon packages are now delivered by an Amazon van or by some guy's personal vehicle with an Amazon magnet on it. I believe they're a mix of the Flex[1] program the author referred to and private companies Amazon is contracting[2]. Not a stretch to see them adding pickup as a service and competing directly with USPS, UPS, FedEx etc. See also the companies they're acquiring in this area[3].
[2] https://logistics.amazon.com/
[3] http://www.seattletimes.com/business/amazon/amazons-delivery...