News is breaking today that Amazon is now enabling customers to drop off return shipments at Amazon Lockers. One report indicates that this shipping option has been in place since September 2013, though it appears that the option escaped press notice until this week.
Amazon has been installing the lockers in public locales in the US and UK over the past few years, thus solving one of the perennial problems that annoy both online retailers and their customers. Namely, UPS and most other delivery services make their rounds during the day, when most people are at work and cannot sign for a package. By setting up lockers and letting customers ship items there, Amazon makes it much more convenient for customers to buy more stuff.
I haven't had a chance to use or even see an Amazon Locker, but I have seen the USPS lockers at my local post office. Resembling the quarter-operated lockers at gyms, the USPS Parcel Lockers enable you to pick up a package at a more convenient time. The USPS started deploying the lockers in April 2012, about a year after Amazon.