Read Robin Cangie in her article Facebook Doesn’t Need Mind Control to Control You
She compares Facebook’s new Sponsored Stories application to a panopticon, that is a circular building, originally designed for prisons, that allows outside observers to watch prisoners without their knowing. That creates a “sentiment of an invisible omniscience.”, as Wikipedia puts it
The concept is that you may be chosen to sponsor a story if you named a brand (the company will use you post to promote their product). You know they may be looking to your posts, so your behaviour takes it into account… Not only Big Brother is watching you, all these companies too!