It seem that you are almost always leaking some information without you knowing about them. Tracking the users is the invisible business that funds the web. Also spies target ‘leaky’ phone apps because they transmit users’ private information across the Internet.
Video files can also reveal lots of interesting information that you don’t normally notice. Mystery signal from a helicopter web page by Finnish signal hacker Oona Räisänen tells how helicopter flying route can be extracted from YouTube video. She found that weird interference in the audio on the left channel was not interference at all, but telemetry data that could be pretty easily interpreted. It could be used to plot the the location trace of the helicopter on Google Earth map. Awesome work!