advertisers. another way for them to "gauge" their reach and brand appeal. or something.
literally i feel like every new thing that comes to the browser, a marketer at a company thinks, 'how can we exploit this to put more junk into the face of other people?'
i am not against advertising, i just think most of them have no limits in terms of what they'll exploit at the expense of their own users.
I can also imagine on a lighter note this being used for games where you look to where you want to move a character (maybe blink twice for confirmation).