Google provide more advice on "invalid clicks" this topic talk about ads on pages containing interactive media, such as videos and games. "We understand that video content pages aren't as easy to monetize as regular text-based pages and that publishers are interested in experimenting with different ad placements, but we'd like to clarify some of our policies addressing AdSense for content ads in interactive media environments":
If you're interested in monetizing overlay or in-stream placements on your video content, check the video below. Similarly, if interested in placing ads on interstitial pages on Flash gaming sites, read AdSense for games.
"The key difference between using these products and AdSense for content is that with AdSense for games and AdSense for video, we only show ads from a pool of advertisers who specifically target these kinds of placements and have optimized their campaigns and creatives towards them," explained Google.