Some folks tend to speak to peers, other's turn to official memo's, others talk radio, etc. There is good evidence that these are somewhat culturally specific. A perfect knowledge management system must interface these types. It is partly the mixing that creates innovation. Also, look back at this discussion forum.
Old streams are pretty much gone.
A more perfect system will automatically link new thoughts to old postings so that forgotten ideas remain alive. And that, I belive is the very crux of a knowledge management system. One the fallacies is that managers know what information they need.