Tag tag tag
Seemingly, given the freedom of folksonomy, people tend to move from hierarchical "folder" modes of tag interpretation (one-to-many) towards more open "keyword" modes (many-to-many).
Keywords are flat, many-to-many, open; folders are hierarchical, one-to-many, closed. (In short, folders are bad, m'kay?) But what does this really mean? If I think that tags are 'like' keywords or that tags are 'like' folders, what difference does it actually make?
From Tom's original piece:
Matt's concept was quite close to the way tagging is used in del.icio.us - with an individual the only person who could tag their stuff and with an understanding that the act of tagging was kind of an act of filing. My understanding was heavily influenced by Flickr's approach - which I think is radically different - you can tag other people's photos for a start, and you're clearly challenged to tag up a photo with any words that make sense to you. It's less of a filing model than an annotative one.
Incidentally, "an individual the only person who could tag their stuff"? That's Technorati rather than del.icio.us, surely?
But anyway - the main question is, what are you actually doing differently if you use a tag as an 'annotative' keyword rather than a 'classifying' folder? In either case, it seems to me, you're pulling out a couple of characteristics of an object and using them to lay a trail back to it. The only real difference I can see is that you'd expect to have more 'keywords' than objects and fewer 'folders' than objects, but I can't see how this changes the way you actually interact with the tags or the tag-holder services - or the objects, for that matter.
Perhaps I'm just not getting something - all enlightenment is welcome. But I suspect that, in practice, Flickr and del.icio.us and... er, all those other social tagging services... are converging on a model somewhere between 'keyword' and 'folder'. The tag cloud is crucial here. Flickr may start by enabling you to "tag up a photo with any words that make sense to you", but the tag cloud display "conceals the less popular [tags] and lets recurrence form emergent patterns" (as Tom notes here); it also prompts users to select from previously-used tags if possible. Conversely, the (more rudimentary) tag-cloud display in del.icio.us gives less-used tags more prominence than they had when they were left to scroll off the screen, prompting users to select more widely from previously-used tags. In effect, the tag cloud draws del.icio.us users away from big-tree-of-folders thinking, while also drawing flickr users away from the keyword-pebbledash approach.
[No, that wasn't my promised post about the Long Tail. (It doesn't exist, you know.) Yes, I will get round to it, some time.]