Malaysia Airlines Flight 370
As the search for Flight 370 moved into the Southern Ocean, 6.3 million people were still clicking their way though satellite images. So far there have been over 485 million map views and the crowd has tagged over 6.7 million features, many of which (thanks to excessive plastic pollution in the ocean) are literally garbage. While Tomnod and DigitalGlobe meticulously compile the tags, the sheer quantity of information they're managing is mind boggling.
Not only is the search area huge and undefined, but the number of items that are identified, plus weather and drift patterns, means it may take days (or weeks) for searchers to find them and check them out. Meanwhile, expert technicians have a bit of an edge on the volunteers. Using a variety of tools to analyze the images, experts are able to rule out more of the non-plane debris and focus on objects (such as those in the Southern Ocean) that are a better match.