That would be a really big undertaking. I think it would be fun. You know, we’ve joked around the pool table about “Wouldn’t it be great if we crawled the web, found all the images, and ran OCR on all the images on the web?” That really would be a lot of work. I think it would be a fun idea, but I’m not sure that you should count on that in the short term from Google.
by Matt Cutts - Google's Head of Search Quality Team