'Share' button on DualShock 4 will allow game spectating and other features
Moments ago, Gaikai CEO David Perry confirmed that a 'Share' button on the DualShock 4 controller will allow you to share your gaming experiences with other PS4 players instantly.
Specifically, you can stream what you're playing to other PS4 gamers. In turn, this will allow other players - friends and public players - to leave comments of encouragement (or disdain!) on your stream.