From a Post on the Google Operating System Blog:
Google sent the following message to everyone who uploaded videos to Google Video:
Later this month, hosted video content on Google Video will no longer be available for playback. Google Video stopped taking uploads in May 2009 and now we’re removing the remaining hosted content. We’ve always maintained that the strength of Google Video is its ability to let people search videos from across the web, regardless of where those videos are hosted. And this move will enable us to focus on developing these technologies further to the benefit of searchers worldwide.
On April 29, 2011, videos that have been uploaded to Google Video will no longer be available for playback. We’ve added a Download button to the video status page, so you can download any video content you want to save. If you don’t want to download your content, you don’t need to do anything. (The Download feature will be disabled after May 13, 2011.)
Alex Chitu also makes an excellent point:
It’s really disappointing to see that Google doesn’t provide an option to migrate your videos to YouTube. In fact, this option should’ve been available two years ago, when Google Video became a search engine. There are about 2.8 million videos hosted by Google Video and it’s hard to believe that all of them will be manually uploaded to YouTube.