How McDonalds touch screens create dirty stores. Lessons in unintended side-effects when you think you have a genius idea to cut costs and lift revenues.

And now McDonalds are letting customers down on the things they've relied on for decades. "All that’s missing is a bucket bong on the straws-and-napkins counter."

Links:

Rory Sutherland on why Usain Bolt trains on Chicken McNuggets

More Rory on why guys buy more burgers from touch screens

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