Late last fall, in the gleaming white lobby of Madison Square Garden, uniformed attendants were posted at security stations to make thousands of smartphones stupid. Chris Rock was playing his 10th show in a 12-city international tour, and at every stop, each guest was required to pass through the entryway, confirm that his or her phone was on vibrate or silent, and then hand it over to a security guard who snapped it into a locking gray neoprene pouch—rendering it totally inaccessible.

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