"Unlike article extraction, it doesn’t seem anyone anywhere has ever put a lot of thought into getting thumbnails out of a website." Incorrect. Diffbot does a

"Unlike article extraction, it doesn’t seem anyone anywhere has ever put a lot of thought into getting thumbnails out of a website." Incorrect. Diffbot does a visual analysis of the page to determine the best thumbnail. [edit: I also get the impression that Prismatic does intelligent grokking of the thumbnail image, especially because I know the team, but I'm not aware of anything they published about their methodology.]