We need to tackle the cause of the problem. In this case, treating the symptoms is the behaviour they want.
What happens when I'm tagging a photo but listening to music at the same time?
Or I run the photo tagging software in a small window and watch a movie (or some porn) instead?
So they can create tags from brain waves, but there's no way to tell what a user is actually focussing on.
As a incognito porn site surfer, I was really taken aback and worried about privacy issues.
Interesting choice of words. Chrome has an "incognito mode". From the blurb shown when you open the browser in that mode:
Pages that you view in this window won't appear in your browser history or search history, and they won't leave other traces, like cookies, on your computer after you close the incognito window. Any files that you download or bookmarks that you create will be preserved, however.
All constants are variables.