GCHQ intercepted webcam images of millions of Yahoo users worldwide
This really isn't any worse than the other invasions of privacy that have been revealed – but it's much easier to point at it as an egregious and visceral violation of privacy. Even though webcam stills may be the least important (or useful) spying the US and UK have been doing, this may be some of the best fodder for arguments to limit such activities. So thank you, UK, for being so dumb.