In their continued integration with other Yahoo! properties, Flickr has added a ‘Find Similar Images on Yahoo! Image Search’ link to their tags pages. What interests me is the search string that is automatically built into that link.
Looking at the tag page for ‘san francisco’, the link doesn’t go to the Y! Image search for just that tag, it is an automatically-built complex query (san francisco california OR bridge OR goldengatebridge OR goldengate OR alcatraz) which appears to be created using Flickr’s automagical tag-relations building feature. It’s calculating that those other words are related, so it’s including them in the search to broaden the result-set. Pretty cool!