With the release of a ton of innovative products such as Office 12, Exchange 12, and Vista–Microsoft has decided to sit on a product rather than release it. Knowledge Network, previously an add-on component to Microsoft Office SharePoint Server, will not be released as a full blown supported product or even as an add-on product; but as a "Technical Preview".
According to the KN Team: "As a Technical Preview, KN will still be available to customers as a web download at no additional cost and will include documentation and community support. However, Technical Previews are not supported or covered by standard product support services or warranties. "
The key is "Community Support". In other words, Microsoft won’t help you if you have issues.
Another blogger by the name of MikeG (a MS guy) thinks that this will open the door for IBM’s project named "Ventura". We shall see if Big Blue decides to integrate with SharePoint. Doesn’t seem likely, this is just what Domino needs.