> The idea that MACs should be somehow private because someone found a novel use for them doesn't even pass the laugh test. IP addresses are not "private". Your face out in a public area is not "private"
I think you might be misunderstanding the part of this I have a problem with, or perhaps my language wasn't explanatory enough. I have a problem with the company linking back this info to a specific person, not the information itself.
MACs shouldn't be "somehow" private. MACs are not private. But when you use them to tie back to a specific person who is in your shop (with the credit card purchase info), you are essentially tracking a person. I think this activity should be regulated and should be an opt-in thing for users. (Enforcing this regulation could be admittedly a challenge, but it will at least be a step in the direction of strongly discouraging businesses to implement such 'features'.)
Similarly, your face out in a public place is not private. But if I have a startup that sets up CCTVs in participating businesses' premises and then track the movement of specific customers from shop to shop and generate data like "Okay -- the same face that was tracked shopping at Nordstrom then went on to have lunch at the Whole Foods next door; and from the credit card that was used, we can see that it was Mr. Karunamon", it's going to run up against major privacy concerns. I think this is very similar, but not that controversial because it is not so visible.