Robert Ott showed off openID. If you wondered about these strange links which start to pop up all over the web near the login buttons, openID is a way to register yourself once at a place you trust and then use that to login elsewhere.
The idea behind openID is that you click on the link, the web site passes you on to an identity Provider which can use any means to make sure you are you and then give that confidence back to the original site. See the openID.net website for details.
The cool thing about openID is that you just have to manage a single identity and use that to log in into various services on the net without giving all of them the same password (and thus make you very vulnerable agains attacks). The main problems which openID doesn't solve is stalking and spamming.
openID makes stalking easier because you have to enter your openID at every place you want to log in to. Same id means same person. There are talks in the openID community to allow a person to have more than one ID and still use the same identity provider but there is nothing definite, yet.
Also, openID doesn't protect against spammers. It might help, though, because of two things: a) You can black list identity providers which allow spammers and b) you can send the police to the other identity providers which will hand over the real identity of the person behind the openID to the authorities on court order. So this might help in the war against forum spam, we'll see.
All in all, a good talk.