Google has announced that it's rolling out "click-to-play" video ads for AdWords. If you doubted it before, you can't question anymore that we're in a video boom right now. As with the other image and flash based ads, advertisers can pay on a CPC or CPM basis, and site targeting is available.
What Google's touting as an advantage is the "click-to-play" aspect of the user experience. These videos will not begin playing automatically, rather they will rely on users to initiate the video experience. After that initial click, any other click on the unit takes you to the advertiser website. Keep your eye on this one.
Read it all on the official Google "Inside AdWords" blog.