The most interesting presentation at the yesterdays London Wiki Wednesday was a talk by Alan Wood and it was not about a wiki - but something more like an interenet forum (or biulettin board system or ... whatever).
I was always of the opinion that there is much unrealized potential in this old software genre.
It is message based - like email or RSS - so in fact it fits better the conversational nature of most communication then document based wikis. But it is also centralized - and that means you can do many things you cannot with a decentralized system (like version control of attachments, uniform visualisation of the conversations - i.e. less need for quoting, moderation, statistics etc.). All the talk now is about Social Networking Sites - but in fact the networking part is so insignificant in all of them - and most of the interaction that happens there is exactly the same as you had on internet fora and BBSes.