Darren Barefoot rants against tags, perhaps a bit hyperbolic (but a welcome tonic these days). There’s a gem in the first comment though:

…tags only work well for individuals who know what they will tag something with. That is, if I need to find a URL or know I linked to something that’s related to something else, then I search for a tag that, based on what I know about myself, I would use to categorize it. Aggregating individuals’ tags to determine what the category something belongs to so far hasn’t delivered on its promise, which is a “wisdom of crowds” of categorization.

Tagging may seem more social than it really is. Food for thought.