In some ways, a lot of Channel 9 exists as it is now due to that very fact. When it originally launched (before I was on the team) it was using ASP.NET, before ASP.NET was officially ready for production. I believe that was one of several reasons why Channel 9 essentially was a rogue entity at Microsoft, not at all against policy, but unable to run within the existing web-site operations structure of microsoft.com because it was built using pre-production technologies.
This is a tradition we've continued though. We launched Silverlight support before it was RTM'd, we used ASP.NET MVC before that was RTM'd, for a while we ran pre-release versions of Expression Encoder and we are now using Azure CDN features before they are RTM'd. We are just 'special' that way