Here's a fascinating idea that's been around for a few years: Digital Dead Drops.
In spycraft there's the concept of a "dead drop", a place where one person can secretly leave something for another person to retrieve so that the two parties can avoid meeting. For example, a loose brick in a wall could be used to hide a letter of a package.
A modern, public version of using dead drops called "geocaching" came about with the availability of consumer GPS devices. In geocaching, which is similar to the much older pursuit called "letterboxing", the locations of caches are specified by latitude and longitude values and usually require some degree of searching when the target area is reached. The goal is to sign a logbook and sometimes there are objects in the cache to retrieve and the requirement to leave new objects.
But, of course, technology moves on and the latest incarnation of dead drops is digital. These drops consist of USB drives usually cemented into walls with just the connector poking out. The idea is to leave and recover data files (or executables though not a good idea) stored on the drop; these files could include any kind of content you can imagine and the result could be thought of as anti-cloud storage.
A digital dead drop cemented into a wall
The digital dead drops concept was started in the US by Aram Bartholl, an artist from Berlin who was doing a residency in New York in 2010. A similar system had been installed in Germany in 2009 and Aram started the US version by creating five dead drops and announcing the idea online:
'Dead Drops' is an anonymous, offline, peer to peer file-sharing network in public space. USB flash drives are embedded into walls, buildings and curbs accessible to anybody in public space. Everyone is invited to drop or find files on a dead drop. Plug your laptop to a wall, house or pole to share your favorite files and data. Each dead drop is installed empty except a readme.txt file explaining the project. 'Dead Drops' is open to participation. If you want to install a dead drop in your city/neighborhood follow the 'how to' instructions and submit the location and pictures.
Eventually a web site, deaddrops.com, was created where drops could be registere. Since the original announcement thousands of dead drops have been added including wireless drops, dog drops (a USB drive attached to a dog's collar), skateboard drops, and flying drops mounted on on quadcopter drones. There are even mobile apps available to help you find drops!
Deaddropdog (or "Filesharing-Hund" in German)
Obviously you have to be careful when you access the contents of a digital dead drop; if you don't disable autorun and virus scan everything you retrieve you'll be making a big mistake.
I just checked the map on deaddrops.com and I see there's a couple of drops just up the road from me. I think it's time to take a break.