This one has had quite a bit of coverage, but it's such an interesting concept I think it's worth a mention. Berlin-based artist Sascha Pohflepp's Buttons camera is a device designed to capture a moment rather than a picture - that is, it separates the content & location of a point in time from the chronology of it. Pressing the shutter-release causes Buttons to search for a photo on Flickr that was taken at that exact same moment, and it's that image that is displayed on the viewfinder screen.
You could dismiss it as a somewhat hokey arts project if you were so inclined, but Pohflepp is keen to stress the interconnected network between individuals - two people so moved by their environment that they choose to capture an image right then and there. All of a sudden photography becomes a collaborative effort in a way far more personal than simply showing your friends and family an online album.
"After a few minutes or hours, depending on how soon someone else shares their photo on the web, an image will appear on the screen. In a way, it belongs half to the person who had pressed the button and still remembers that moment. Because of that connection, the photos are never dismissed as random, no matter how enigmatic they may be" [Sascha Pohflepp]
Buttons is reminiscent of Sketch Swap, where online artists draw a picture and, on hitting Submit, receive an image drawn by someone else in return. Of course, in both scenarios fate plays a great part - will you get a masterpiece or a monstrosity? A second either way could change that.