When you talk to Siri, Cortana and Google Now, who's listening?

If you so choose, you can delete voice items one at a time or purge all of them from the same page, which can be found in the depths of your Google account online. Actually, deleting all your voice clips doesn't purge them from Google's system. On my Voice & Activity page, I find each spoken item presented with a button next to it, allowing me to play the voice command back or delete it entirely. I can see why companies like Apple and Google want to work with spoken commands because speech recognition can only get better when computers confront more and more speech.