I thought I should point out a good, real-world exmaple of the potential benefits of this. Completely coincidentally, we (the Library of Congress) announced today that we have discovered some previously unknown and extremely rare photos of Lincoln's second inauguration.

That discovery was made in part by a user of our Web site who was looking at some existing images that were thought to be of another event, and then investigated and confirmed by our curators. (LA Times story here.)

Now imagine if we could take all 14 million photos in our collections (a Herculean task, I know) and harness the community and the great technology at the heart of Flickr. Who knows what discoveries would lie in wait?