But, aren't ecommerce sites collecting this information and more from your browsing? I don't think it's possible to say one is much better than the other, just that we expect tracking online, not in the real world.

There is the point that in the "real world", social norms haven't yet adapted to the requirements of privacy (although you could also view it as societal norms allowing too much tracking). For example, if I wanted to use a mask to conceal my face from trackers, I would be ostracized. There are analogues in the virtual world of course, but it's usually harder in the physical world.

This also works http://www.instructables.com/id/The-Invisible-Face-Mask-/

some modern cams (at least traffic ones) no longer use AGC and will not be fooled by this

They're even more accurate than facial recognition at building a profile of what demographic you fit in

It's likely traditional retail that falls by the wayside is going to make room for more competitive retail that leverages this information to its advantage in a way ecommerce sites can't.

Consider Amazon Go (https://www.theverge.com/2016/12/5/13842592/amazon-go-new-ca... setting up an account with a store, users enter, grab what they want, and leave. The system of cameras and biometric trackers observing the store figures out after-the-fact what you grabbed and charges it automatically to your account through a sensor fusion including face recognition. That's a level of convenience rivaling ecommerce for things people want to grab by hand (often produce and small items, for example), and it's completely enabled by this category of technology.

Perhaps, but it simply means the survivors will become more desperate to gain an edge. We've seen this exact behavior with online news sources cramming more and more ads and trackers into websites.