with a unique identifier, through the phone, they can learn so much about you, about things you wouldn't otherwise volunteer to them if they tried to do a survey at the front of the store. >> the benefit to the store is they can send you specialized advertising or what? >> yeah. and actually if you actually, for example, nordstrom, other stores have an application so if you have their app and you're in store, bass they know where you're at, they can start serving you up advertising and understanding, some of this technology is so weird it can determine if you're in a bad mood and decide maybe you need beer or whiskey instead of the magazine you were going to buy. they're really getting detailed and that generates privacy concern. how die keep people from tracking me. >> what die need to do? turn the blue tooth or wi-fi off? if you still have your 4g can they do it that way? >> depends on the technology. one of the way nordstrom was tracking you, phones have the wi-fi signal and there's a set that says search for a wi-fi