Quietly, it appears that Google AdSense's rich media inventory is growing nicely... even despite the economic climate which has many online advertisers scaling down. I don't have any hard data to prove the point - but when you default AdSense to display image-only ads, you'll find that video and rich-media units are appearing more quickly and with greater rotation. Many of the ads are pop-culture focused (see the movie preview unit below) - which means that the ads rotate regularly as new shows, movies, etc are being promoted.
Although the screenshot below is at about a 50% size reduction, you'll notice the top leaderboard which is a GM / Google promotion that installs iGoogle gadgets. The "add to iGoogle" button pulses on mouse hover. It's a terrific promotion and the creative is superbly done - enticing users to engage with the unit and explore what the action does (in one case, "adding to iGoogle" and in the other, previewing the movie).
As a publisher, I'm excited about seeing richer, more engaging units on my content.... because, as a consumer, I prefer to see this kind of content.... consequently satisfying the advertiser and making him/her more inclined to grow their campaigns.