Olin talking about uplinks. (Yes, I mainly took the picture to test my new camera mobile phone.)
It was a nifty technique Olin presented clever but simple. After the talk you had a feeling that you completely understood the technique, and it seemed useful for a large class of problems. The main drawback is that the data structure is ephemeral (that is, not persistent), which means that when you perform an update you destructively update the term.