I spoke with my grandmother this morning. She related a story about siting in a busy doctor's reception recently; everyone in the room except her was on a mobile (or 'touching their phones' as she put it). She said that, as an elderly person without the technology, it's often isolating in that kind of situation as there are people all around but nobody is present.
I considered as she spoke (note, distracted from the actual conversation with her and thinking instead about the technology), someone should make an app that connects mobile devices in close proximity with a peer-to-peer chat. People in waiting rooms or packed trains could then communicate about what's happening in that place, share pictures, link up on social networks, just generally get to know each other. It could work over WiFi as the devices can already call out and find each other in an ad-hoc network.
My grandmother, when I attempted to explain this to her, just said, 'or they could just...talk to each other.' Well, there is that; how quaint.