Ask HN: Can retailers scrape information from your smartphone?

Most articles I read on customer tracking indicated that the in-store routers mapped the unique MAC address of any given phone to create a "profile" of the consumer when it automatically connects to the store's open wifi network. I am curious, however, if the tracking methods have become more sophisticated. About a week ago, I visited a mall and spent some time in several clothing stores, including a Gap outlet. I did not buy anything. Flash forward a few days later, and my private Gmail address starts receiving promotional ads from Gap. I've never received emails from them before, as I try to avoid using that address for anything which might receive spam--it is, however, the address which is linked to my Android phone. Is it possible to scrape such information from the phone if the phone connects to your wifi network? It could very well just be a coincidence, but I find the timing of these two events troubling.