According to the Register, Google's working on a project that will use your PC's built-in microphone to monitor what you're watching on TV in the background. With that information, they're going to serve you contextual ads on your browser or desktop (we don't know which) to match the show you're viewing.
Since Google's all for storing information about you, we don't doubt that if they do implement this program, they're going to store all recordings collected for some later project. As if Google didn't have enough data on you already?
Google developing eavesdropping software [The Register]