If I were to use this technique, I would use the following precautions:
1. I would use two domains; a blackhat and whitehat domain The WH domain would be a page containing a legit looking website with AdSense on it. The BH domain would contain our overlay code and would be the domain I would be "promoting" all around the 'net. Instead of putting the AdSense code on the BH domain, I would instead iframe the WH domain behind the overlay image. This way G "sees" all impressions/clicks coming from the WH domain

I would also show a cloaked version of the WH page to the BH page by checking the referer on the WH domain. If the referer is that of the BH page, then return an optimized-for-AdSense version of the WH site to the BH page's iframe.
2. Keep the CTR down by only showing the overlay every so often.
3. Try as much as possible to exclude G's User-Agents and IP ranges from being shown the overlay!
4. Use cookies! Each time a visitor visits the BH domain, and the overlay is presented, a cookie would be set on the visitor's computer indicating that the overlay has been triggered. If the visitor returns to the page in the future, and they still have the cookie, then they will be shown the a real link to the video or whatever.
These methods should make it difficult for G and others to detect...