At this point, everyone knows that Microsoft's Mix event happened this week. I know everyone knows, because they had to take the video downloads offline due to their inability to handle the demand:

We are currently experiencing issues with download speeds and buffering. The demand for the sessions videos has been extremely high and has exceeded our ability to serve these videos up with sufficient bandwidth. At this point, we are going to remove the links and the player from the site to allow our engineering team to push the content out to various media caches around the world. When that is completed (current estimate is 8PM PST) the result should be a much better experience and we will re-enable playback and download. Thank for your patience as we deal with this issue.

If they took all the content, and provided a torrent file with all the videos and slideshows, they wouldn't be responsible for all the bandwidth, the consumers could share the burden. After NDC last year, all the videos were provided as a really large torrent file, and getting the content was very easy. Easier than a batch file with a bunch of curl calls.