...Webcam Images.
http://news.yahoo.com/s/ap/20110504/ap_on_re_us/us_rental_computer_spyware
I once had a friend who would place a towel over the tuning apparatus that he rented from the cable operator.
"Why do you do that?"
"Shhh. Don't talk so loud."
"Why not?"
"Because they are listening to us. But with that towel in place, they can't see us."