Cabela’s, Benneton, and Mothercare are among national retailers that have tested the idea of tracking customers in their stores using cellphone signals and video cameras, according to the New York Times. Nordstrom has also experimented with the idea, but stopped after some shoppers complained.

But with all the other online tracking that goes on, why should we care?

Jonathan Zittrain, co-founder of Harvard’s Berkman Center for Internet & Society, says the tracking could lead to customer discrimination. He joins Marketplace Tech host Ben Johnson to explain.