AP Photo

Last week, I spotted Neil Patrick Harris at a ramen restaurant in D.C. and tweeted about it. I immediately felt a little twinge of guilt about ratting out the star’s location to my Twitter followers… especially after he looked at his phone and started peering around the tiny restaurant, as if he’d spotted my tweet and was looking for the responsible party. This is one of the downsides of being a public figure in the age of instant public communication; their recognizability makes it harder for them to maintain location privacy. But it’s not just the Neil Patrick Harrises of the world who have to worry about their whereabouts being disclosed to third parties by fans; your smartphone is your biggest fan and it’s constantly...