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I noticed this as well and wondered about it.
It is important to distinguish between a network behaviour, such as the folksonomy as described above, and a group behaviour.
A collection of tags may be created in two very distinct ways:
1. people, working independently, just happen to use the same word to describe the same resource
2. people, working together, agree on a term that describes a given (type of) resource
Method number (1) is a folksonomy, and it is a network behaviour. It does not involve collaboration of any sort.
Method number (2) is not, strictly speaking, a folksonomy. It is a method more common to librarians and taxonomers.
We have seen, however, efforts made to organize tags (people will write, "Everybody tag this event 'OCC2007' or whatever).
This sort of organization is arguably no longer a folksonomy, as some people are using a privileged position to instruct other people how to tag (I discuss this in my paper here: http://www.downes.ca/post/14 )
I would not go so far as to use a word like 'collabulary' - that is a ridiculous word, and is not needed to describe something that we already have perfectly good words for, a 'taxonomy' or a 'vocabulary'.
And the author's suggestion that folksonomies ought to be recognized as 'collabularies' is, in my view, a mistake: it either misrepresents what a folksonomy is, or it uses a new word needlessly.
A community of individuals working independently, such as Digg users, is not collaborating. The rankings are not the result of group action. Rather, each person works independently.
Indeed, it is worth pointing out that when Digg members collaborate, the system is deemed to be broken and the reliability of the rankings cast in doubt. And interesting debate surrounds edge cases (such as the case where one person sees that another has Dug a resource, and, trusting the other person, Diggs the resource, not because it is good, but because people who Digg popular resources early are rated higher than people who don't).