I personally don't think there should be any government involvement with tracking individuals, I think it's too ripe for abuse. It makes me think of the Patriot Act where the government used a tragedy as a way to "temporarily" exapand its power, then keeps voting to not repeal it. I think it would be fine to ask people for the zip code they live in, that way if there was an outbreak in an area, the government could get an idea of where those residents were shopping. People could give false info, but I've seen enough people unquestioningly give up their phone number when asked, that I don't think it would be a big issue.