scale|free and many others have suggested Technorati tags = metacrap?
While the world falls in love with folksonomies and tagging, Dare Obansanjo mutters "Bah humbug, seen it all before".
All the problems with META tags are still valid today most important being the fact that people lie especially spammers and that even well intentioned people tend to categorize things incorrectly or according to their prejudices.
This is something that lots of people are discussing, so I haven't felt the need to say anything new. In the discussion on social software last night at KM Chicago (review soon), we hit on an aspect that I hadn't considered before. Specifically, tagging is personal. My set of tags for this blog only make sense within the context of my blog and my interests. Sure, I try to come up with tags that are sensible to the visitor, and I even create short descriptions of what I mean by "theory of constraints." And in groups (where the social arises), my use of tags will certainly be informed by how others use them. But these same tags aren't going to be exactly the same on someone else's blog. The same goes for my Flickr tags, though I do try to use tags that will make sense to my family and friends who might visit.
The problem with the META tag on web pages was that there was some attempt to at a global namespace / categorization scheme to improve search. It didn't work because the spammers figured out how to game the system, but it also didn't work because the page owner had to try to come up with every conceivable "tag" that would connect search engines to their page. Not fun. With folksonomies, or at least with my blog, the goal isn't search engine optimization, but providing information for myself and my visitors. I don't need a globally-accepted set of terms for that. (I recognize that spammers could just as easily abuse tags for "knowledge management" to attract me to their site, but that is only a piece of the value that tagging provides. I will continue using that term to help my internal navigation.)