Folksonomy, a new term for socially created, typically flat name-spaces of the del.icio.us ilk, coined by Thomas Vander Wal.
In commentary on Atomiq, Gene Smith, who generally likes the idea, lists some disadvantages of folksonomies:
* None of the current implementations have synonym control (e.g. “selfportrait” and “me” are distinct Flickr tags, as are “mac” and “macintosh” on Del.icio.us).
* Also, there’s a certain lack of precision involved in using simple one-word tags—like which Lance are we talking about? (Though this is great for discovery, e.g. hot or Edmonton)
* And, of course, there’s no heirarchy and the content types (bookmarks, photos) are fairly simple.
A lot of this parallels the discussion around the continuing development and use of del.icio.us. I am in the “Wenn ich Ontology höre … entsichere ich meinen Browning” camp, so I think Smith’s points are not so much absolute disadvantages as choices.
Synonym control is not as wonderful as is often supposed, because synonyms often aren’t. Even closely related terms like movies, films, flicks, and cinema cannot be trivally collapsed into a single word without loss of meaning, and of social context. (You’d rather have a Drain-O® colonic than spend an evening with people who care about cinema.) So the question of controlled vocabularies has a lot to do with the value gained vs. lost in such a collapse. I am predicting that, as with the earlier arc of knowledge management, the question of meaningful markup is going to move away from canonical and a priori to contextual and a posteriori value.
Lack of precision is a problem, though a function of user behavior, not the tags themselves. del.icio.us allows both heirarchical tags, of the weapon/lance form, as well as compounds, as with SocialSoftware. So the issue isn’t one of software but of user behavior. As David pointed out, users are becoming savvier about 2+ word searches, and I expect folksonomies to begin using tags as container categories or compounds with increasing frequency.
No heirarchy I have a hard time as seeing as inherently problematic — heirarchy is good for creating non-overlapping but all-inclusive buckets. In a file-system world-view, both of those are desirable characteristics, but in a web world-view, where objects have handles rather than containment paths, neither characteristic is necessary. Thus multiple tags “skateboarding tricks movie” allows for much of the subtlety but few of the restrictions of heirarchy. If heirarchy was a good way to organize links, Yahoo would be king of the hill and Google an also-ran service.
There is a loss in folksonomies, of course, but also gain, so the question is one of relative value. Given the surprising feedback loop — community creates folksonomy, which helps the community spot its own concerns, which leads them to invest more in folksonomies — I expect the value of communal categorization to continue to grow.