Microsoft PR privately acknowledged they withheld the video to encourage media and developers to attend in person. Vendor conferences like the PDC and JavaOne have become major marketing events for companies, both for customers and developers. IBM and Novell have piggybacked on LinuxWorld and other open source get-togethers, while the aging dinosaurs (Comdex, PC Expo, even N+I) have collapsed or converged toward the consumer electronics space.
The developer conference business model is easy to understand: Water the developers and the platform will grow. Some analysts (and Microsoft insiders) suggest the PDCs focus on Longhorn was too much, too soon, but developers only had to remember how long Microsoft kept .Net behind the firewall to relish the idea of early access to the next wave.
But each of these spaces is parochial to the larger reality of the network. The OReilly conferences have always leveraged this fact, knitting disruptive technologies together into a loosely-coupled fabric akin to grid computing. The dial tone in this case is frequently serendipitous at first, but with each successive iteration, the implementations become stable and resilient.