"I learned a lot about fandom couple of years ago in conversations with my friend Britta, who was working at the time as community manager for Delicious. She taught me that fans were among the heaviest users of the bookmarking site, and had constructed an edifice of incredibly elaborate tagging conventions, plugins, and scripts to organize their output along a bewildering number of dimensions. If you wanted to read a 3000 word fic where Picard forces Gandalf into sexual bondage, and it seems unconsensual but secretly both want it, and it's R-explicit but not NC-17 explicit, all you had to do was search along the appropriate combination of tags (and if you couldn't find it, someone would probably write it for you). By 2008 a whole suite of theoretical ideas about folksonomy, crowdsourcing, faceted infomation retrieval, collaborative editing and emergent ontology had been implemented by a bunch of friendly people so that they could read about Kirk drilling Spock." --- See also the very last link.

Chairman Bruce annotates a lamentation (which I agree with!) over the fate of delicious, in his usual style.  (And wow, when did the Wired website get so aggressive?  His blog is much more enjoyably read via RSS.)