I worry about augmented reality. It's an appealing technology that seems completely inevitable in the next twenty years. You'll wear eyeglasses that are no bulkier than the regular kind, or maybe even contact lenses, and they'll overlay all sorts of useful information on your field of view. You could have an interactive map, a live news ticker, or notifications of messages—anything you can get on a screen now.
The game-changing thing is not the local-specific overlays (which we've already got) but the utter privacy. No one else would know you're checking scores in a business meeting or playing video games in class. These may sound like silly examples, but I don't think they are. How often have you not checked your messages because it wasn't quite socially acceptable to pull out a phone? With eyeglass-mounted augmented reality, all the inhibitions will be gone.
I'm not worried about safety—maybe cars will drive themselves by then. I worry about a world in which everyone is only pretending to pay attention. Our social lives are founded on a premise that has always been too obvious to need articulation: that people attend to the people immediately around them. To not do that was to be rude, absent-minded, or even mentally ill. That's coming to describe us all. We're heading towards a Malthusian catastrophe. Consumer-level bandwidth is still growing exponentially, while our ability to deal with seductive distractions is stable or at best grows arithmetically. We will need to invent a new social infrastructure to deal with that, and I worry that we don't have much time to do it.