I worked in an electronics store (regional, not Best Buy, and out of business now) in the mid-2000s that had this exact measure.
In my store, on busy days, the manager would occasionally "greet" customers at the door for 10 minutes at a time. Coincidentally, the spot he would choose to stand would block the sensor, so instead of 20 customers coming in in 10 minutes, it looked like only 1 had come in.
