The NYT (and C-SPAN, apparently) uses it to identify members of Congress:
https://open.nytimes.com/how-the-new-york-times-uses-softwar...
Shutterfly is apparently using it for image categorization:
http://ir.shutterfly.com/news-releases/news-release-details/...
I uploaded about 120k photos including all my father's photos I had scanned. (about 4000)
I injured my toe when I was 10yrs old. Searched in my Google photos "toes". Found the picture pretty quickly. Have had similar success finding pictures of my childhood dogs. Can also search by people (face recognition).
It's still got a long way to go but I love it when it works.