A Flickr Patent
This seems to be an interesting patent:
Interestingness ranking of media objectsAbstract
Media objects, such as images or soundtracks, may be ranked according to a new class of metrics known as "interestingness." These rankings may be based at least in part on the quantity of user-entered metadata concerning the media object, the number of users who have assigned metadata to the media object, access patterns related to the media object, and/or a lapse of time related to the media object.
I haven't taken the Patents course yet, and I don't expect it will make me instantly adept at grokking patents once I do take it. But if I read the description correctly, Flickr/Yahoo! are laying claims to an algorithm or method of ranking based on user-generated metadata/tagging. It's, dare I say it, interesting.