Walk around a mall. Watch the number of people using their phones to take photos, talk to their friends about options, phoning home to check they're getting the right thing, etc.
For example - you build the social hot-or-not for clothes purchases. How much is the data from that worth to a high-street retailer as a way to guide their pricing and stocking decisions.
(and - come to that - I see folk well out of their teen years doing this. Women especially in clothing stores... and what is the purchasing power of groups who are rich enough to afford smart phones in the first place)
Thanks for sharing this.