The document discusses how audiences are using social media like Twitter to create "backchannels" during presentations. A backchannel allows audience members to communicate with each other and provide feedback to presenters in real time. While backchannels can benefit presenters, they can also be distracting for audiences not participating and potentially hurt presenters if negative feedback is shared publicly. The author examines how backchannels on platforms like Twitter are changing how audiences engage with presentations.