Good thought @caketin but I presumed it was trigger devices that...

Good thought @caketin but I presumed it was trigger devices that were used to determine that you were in the vicinity. If that is so, that data, your location, would be only known by the people who owned the trigger devices. And if I were JB Hifi I would not be handing that data on to the opposition.

Yes, this whole idea of target marketing is getting to be quite obtrusive.
I made the mistake of checking out the price of an air ticket to Saigon with a number of carriers.
Now, no matter where I go on the net, I am served targeted ads by Malaysian Airlines (who were not the cheapest) for fares to Ho Chi Minh City.
Smart of MA, but annoying for me, as it was a passing thought rather than an intention - and I want my IP address back.