Video adsense units have not been performing well and now Google is pulling the plug. It is a shame in a way because they could have worked if the implementation had been better.
As far as polybore could tell they were just a YouTube video unit with a contextual adsense ad on the player. Perhaps if the quality of the videos had been better and the publisher had been paid per video view rather than by click things would have worked out better.
Here is what Google says:
We're writing to let you know that we'll be retiring AdSense video units at the end of April. After reviewing this feature, we've found that it hasn't been performing as well as we had hoped, so we've decided to focus our efforts on other opportunities to help publishers monetise their sites.
We recommend that you begin removing the video unit code from your pages as soon as possible, to ensure that you can take advantage of the available ad space on your pages. At the end of April, any remaining Leaderboard or Skyscraper video units will begin directing users to YouTube.com, while other video unit sizes will automatically be changed to standard embedded YouTube players. These standard video players will display top YouTube videos, but you won't generate earnings from them once this change occurs.
If you'd still like to display free video content from YouTube, you can do so through YouTube.com directly: visit any specific video page for the embed code or sign in to your YouTube account to create a playlist. For more information about embedding YouTube videos, please visit http://www.google.com/support/youtube/bin/answer.py?answer=57788&hl=en_GB. Alternatively, if you have fewer than three ad units on your page, you may prefer to replace your video unit with a regular ad unit.
Although video units are being retired, other video offerings within AdSense aren't affected. Video ads may still appear on your pages and AdSense for video is still available for eligible publishers. If you'd like more information about the retiring of video units, please visit our Help Centre at https://www.google.com/adsense/support/bin/topic.py?topic=12182&hl=en_GB.
Thanks for your support of video units in the past, and we appreciate your patience and cooperation.
The Google AdSense Team
RIP Adsense video units.