stahl: david mcmullen is the c.e.o. edpepper, a nashville marketing firm developing an app called facedeals. as we walk into a bar, this camera identifies me using facial recognition. >> mcmullen: and this will actually be the moment when i got a deal. how did you... >> stahl: i got... i don't know. something just came up on my phone here. ( beep ) oh, my. look at that. "welcome, lesley. get a free diet coke with a purchase of a caesar salad." my, my. my cell phone knew i liked diet coke because in the three seconds it took to walk in, the camera at the door matched my faceprint to my facebook profile, where redpepper mined my shopping history and facebook "likes" to send me the perfect deal. they did that only after i "opted in" or explicitly gave them permission. but if you're queasy about trading your privacy for a diet coke, mcmullen says we've already given up our privacy; cameras in stores, our phones with g.p.s. locators and our credit cards all know where we are when we shop. >> mcmullen: all these things are tra