Last month Google Video started to index videos from third-party sites like Metacafe. The most interesting part was that the site offered "previews" of the videos, but they were more like the full videos. The practice was beyond fair use because Google served the entire video in a Google Video player inside the search results page. Google even hosted the FLV files, probably for performance reasons.
Now Google Video shows 15 thumbnails from the videos indexed from third-party sites and the only way to watch the video is to go to the original source.
Blinkx, another video search engine, shows a 25 second preview for most of the videos, while Yahoo Video shows only one thumbnail for third-party videos.