So Lydia has posted a call for chairs. This, of course, allows me to launch the "I'm chairing at Akademy" button which is done in the style of Paul Adams. Also, an image search turned up a creepy sheep chair -- perhaps we should get one to use for interviews? Chairs do some of the footwork -- ensuring that the switch to the speaker's laptop goes smoothly, optional introductions, managing the time allotted for the talk and dealing with questions. And, if need be, you ask a question yourself. And then you thank the speaker.
When I chair a session, there are certain, shall we say, additional attributes in use. Those fall under "speaker motivational items" or incentives. I'm sure you'll run into them at the conference.
My own talk is saturday at the end of the day, so if you want to motivate me then here's your chance (although you will miss Henri's talk in the process). Don't hesitate to contact the Akademy folks, Lydia in particular, if you need more details on what a session chair needs to do.