There's way too much cynicism here and a lack of insight as to how consumer retail works.
'Privacy invasion' aside there's a lot of obvious benefits to this.
1) Impactful Displays - this will increase sales. In your local coffee shop, going from the static nice pictures, to 'active displays' unambiguously generates more attention.
It's a little bit like having 'nice photo' menus vs 'empty menus' for regular dining. Obviously a nice restaurant doesn't want that - but for everything else, it helps turnover.
2) They can make the 'presentation layer' spiffy without having to worry abut what's underneath. A lot of effort goes into making sure everything looks 'right' on the shelf. Any kind of disorderly shelf gives customers a bad impression.
3) Easy pricing changes. My local 'Drug Mart' they have the 'pricing girl' constantly changing tags. I literally recognize the woman. With the prices on a display, it makes it much easier to manage.
4) Creative possibilities: beyond just displaying 'what's inside' there will be other opportunities. Possibly more detailed product information.
My biggest concern would be frankly the size of those screens and their cost and maintenance - and would the added benefits work out in the metrics. For 3 mid-sized screens at your coffee shop - yes. But for 10-20 large screens (that move, and could be broken) in the back of your grocery store, maybe not.
This is definitely a worthwhile retail experiment.
I suggest we may be seeing a lot more of this in the future.
Maybe not, but it's entirely possible.