I think this is a useful initiative: the Library of Congress is releasing photos to be tagged on Flickr. More from HeyJude! And Tim Stahmer addresses head on the criticisms: "Many were along the lines of 'So, what? All of them are on the LOC site already.' or 'Big deal! It's only a very small part of their collection.'." My own take is that the only way to get them tagged was to release a relatively small number - asking people to tag 4000 images is reasonable, asking them to tag many more will just leave them daunted by the sheer scale of the task.