OK, we know I'm a sucker for an application with a cute name. So I'm a delicious fan. I'm also a librarian, so I collect information in the e-verse as well as in real life. And at least in theory, I'm a fan of folksonomies, G-d knows I defend them to my sweetie (who holds that folksonomies are the beginning of The End) about their usefulness often enough.
I have a delicious account. Haven't used it in a while, because I can't get IT to download the teensy bit of software that would make it easy to do so from each webpage [insert rant about inflexible computers at work here]. So I opened it up and started looking at the 100+ links that were there from late 2008. And, being a weeder, the first thing I did was junk a bunch of stuff that's irrelevant. Then I started looking at my tags. And they were a mess, but worse than a mess, they were not useful. They added nothing to the searchability of the links, and I spent some time wondering what the heck "development.readings" was about, anyway. And this is my problem with relying on folksonomies.
Harking back to Library School, it is exactly this problem that controlled vocabularies are supposed to address. If you define your terms, and terms are standardized, in theory it makes items more findable, rather than less. Which works great if everyone knows their way around LCSH, aka the Big Red Books. Of course, not everyone gets LCSH (cookery, anyone?) and folksonomies, and customer-driven tagging, are incredibly useful to supplement standardized cataloging (meta-data-assignment, whatever).
I'm not ready to favor folksonomies over standardized taxonomies. Not until my tags are still useful a year after I've tagged them.
Oh, and I'm sdentan on delicious. I haven't done much with the social side of delicious, it's more a web-based favorites list for me now, but I'm not averse to sharing!