Earlier quoted context omitted.
You choose to turn on the feature. The people around you have no choice at all if they are recorded or not.
How is this different from Shazam? I don't think very many people are paranoid about their conversations being recorded when someone in a bar holds up their phone to identify what's playing.
Same reason why recording video with a phone (for which you have to hold it awkwardly, or you’ll just record the ground) is different from recording with Google Glass (at first, no one notices if you record or not)