The general idea is to invite 4-ish people onto a panel and have them talk on some subject. The invitees are not told more than a day in advance what they'll be talking about, and it's considered against the goals of the conference to do any real preparation on the subject. The panels are cross-disciplinary, so the it may be Roger Ebert on a nanotechnology discussion or Henry Kissinger on a talk about contemporary Jazz (though it's equally likely that they'd be talking about silent movies and international diplomacy, respectively). Anybody been? I have not yet, but keep meaning to.