"There is no "database" today to associate the device MAC back to any personal information."

You can _say_ that, but the marketing-hacker in me is already thinking about how to hook the wifi MAC address to the credit card payment database, and how to run in-store specials "Like us on Facebook via our free wifi to get $super-special-deal!"

I think saying "There is no "database" today … " is disingenuous at best. I would bet with 100% certainty that someone, somewhere, has been collecting and correlating MAC addresses and individual's identities, and is almost certainly selling access to exactly that database.

(Cynical thought, what're the chances that Apple aren't, right now, already doing realtime lookups on the purchase histories of the original owners of wifi capable iOS device that arrive in their stores with the wifi switched on?)

I should've clarified - there is no database today that is accessible to retailers and/or tracking software vendors. Device vendors like Apple certainly have a database that maps device UDID/MAC to your personal information, but they are very serious about protecting it. Today :)

Actually, there is.

In the better retail video systems, video is time-synced with the registers. I'm not sure how many are doing it right now, but indoor tracking and indoor mapping people would be foolish to not sync their data with the registers as well.

Put another way...

It is a trivial matter to know that it was your phone at the register when your debit card was used.

But they would still only have MAC address and charge, credit or debit card info.

Of course... that may be all they need.

... and the ZIP code they asked for when you checked out.

Sure there is. Remember how your iPhone had to be activated with the carrier?

Or how all that analytics software would use the MAC either as a UDID, or to derive one?