Big venues like football stadiums can contact your mobile phone company and get contact information for all the people who brought a cell phone to the event. B

Big venues like football stadiums can contact your mobile phone company and get contact information for all the people who brought a cell phone to the event. Big casinos have crazy video surveillance but I think there's still a lot of humans in the loop. They've got the budget for it, after all. Of course, the easiest way to track people and their purchases is to sign them up for the store loyalty program and offer them nominal discounts. Works for grocery stores, at least. Bike stores are trickier. Fewer repeat customers.