But we're not just talking shopping experiences here- the data, algorithms, and extra tracking that fuels the (perhaps extreme) future I described above has costs, mostly in personal privacy. Maybe I don't want the conglomerates (and the government, since we all now know they've got their 'black boxes' in the datacenters) to know my penis size, how good my relationship with my father is, what medical conditions I have, and just about everything else one can think of. However, this is the future we're headed towards.
Secondly, I think _greim_ said it very well in this post elsewhere in the thread: "Giving marketers deep psychological and behavioral insight increasingly enables them to circumvent rationality and "hack" consumers in various ways." There is a fine line, I think, between offering exceptional shopping experiences and manipulating your customers.
Once they have that, your MAC address becomes personal. They know what that MAC buys, how long they spend in the store, how much they spend in the store, how often they visit, etc.
Couple that with the fact that with enough WiFi APs, you can triangulate a certain MAC to a specific location in the store, match with the cameras, etc. Probably track you to your car if they wanted with their satellites watching their parking lots.
And then we get into the problems created when these stores either start sharing this info, or the vendor they hire to install their tracking system starts approaching full coverage of the nation / developed world.
Keep in mind this isn't 'crazy future minority report' stuff. These are all things they are either doing now or could easily do now. All in all, it's just another damn piece of info about me that was once personal and now no longer is. "The amount of time Ben Reaves is spending looking at adult diapers is trending up. Flag their profile for incontinence."