Many years ago, I started writing a couple of sci-fi novels. One of them was called Off-camera, a story about the near-future in which everything (and I mean everything) is recorded. In that story, a company called DownTime becomes a huge multinational from harnessing - you guessed it - the downtime of billions of home computers.
(Strictly speaking, it was badly named. Downtime means switched off. But hey, the 'IdleTime Corporation' sounded worse...)