Free transcription of part of the talk:
[…] give a rat a lever that dispenses food pallet every time and he’ll get one when he’s hungry. But if you give one that only sometimes dispenses that food pallet, he’ll just hit until he runs out of steam because he’s not sure of what the trick is and he thinks he’s gonna get it if he keeps banging on that lever.
To see how this applies to facebook, replace the lever with you posting some bit of hitherto private information on facebook, and the food pallet with the jolt of feedback you (sometimes) get as a result of what you have posted. Scary thought, isn’t it?
EDIT: I corrected a number typos I did when transcribing…