Josh Clark (emphasis mine):

Mobile isn’t just ‘mobile’. It’s also the couch, the kitchen, the three-hour layover, all places where we have time and attention to spare. 42 per cent of mobile users say they use it for entertainment when they’re bored. Those aren’t 10-second sessions. That means we shouldn’t design only for stunted sessions or limited use cases.

Say it over and over until you’ve exorcised the mental image of your user typing furiously on her iPhone as she frantically runs down a crowded sidewalk, looking for her next 10-second morsel of information. That user undoubtedly exists, but we have to stop assuming this is the only mobile use case.