Sounds like Wikipedia. :)
Perhaps just some kind of reference system, so when an old debate reemerges, people can just refer to the online record until new ground is broken. The problem in this case is succinct yet meaningful summaries of the debate.
Looking at how well a site like Stack Overflow is working gives me hope of a happy medium between rigor and usability being possible in the future somehow.
It combines a whole bunch of ideas from social sites such as voting, points, awards, wiki style editing into an effective solution. Far from perfect but useful which as about all you could ask for I guess.
It would also be interesting if a company like Disqus started experimenting with features in this area.