Microsoft filed for a patent to detect number of people watching video on a console:

http://www.wired.co.uk/news/archive/2012-11/07/microsoft-pat...

You think people, or enough people, don't watch TV any more?

Consumption of TV has moved almost entirely to platforms that can track that data themselves (for example through a set top box or directly on the web), without requiring someone to have a smartphone turned on, running spyware, in the room.

I think this data is still useful because there isn't a one-to-one correspondence between those devices and the viewers. A box might be left on with nobody around, or it might be the center of a viewing party with twenty people. They also want to know who is watching, since demographics count for a lot.

And the people using such invasive apps aren't the people running those boxes, either, so they don't have access to the data.