Elaine Peterson wrote a commentary on the philosophical issues of folksonomy (or social tagging) in D-Lib Magazine. Based on relativism, she argues that the relativity of social tagging is individualistic.
The issue is that adding enough of those individual interpretations through tags can lead to inconsistencies within the classification scheme itself.
Some advocates of folksonomies have recognized that a democratic approach to Web cataloging also contributes to the abundance of irrelevant or inaccurate information, usually referred to as “Meta Noise”. Meta Noise can be inadvertent (spelling white horse as whit horse), inaccurate (tagging White Horse when the image is of a white cat), or irrelevant (using an esoteric tag known to very few). Overall, many will view folksonomic classification of the Web, as Weinberger does, as “messy and inelegant and inefficient, but it will be Good Enough” 
A folksonomy universe allows both true and false statements to coexist. Because tags are relativized, personal, idiosyncratic views can coexist and thrive in the form of tags, in spite of their inconsistencies. Readers of texts on the Internet become individual interpreters, despite the document author’s intent.
Related to this is the problem of hermeneutics when multiple interpretations abound. As Eco once observed, “while it is a principle of hermeneutics that there are no facts, only interpretations”, this does not prevent us from asking if there might not be “bad” interpretations. Because to say that there are no facts, only interpretations, certainly means that what appears to us as fact is the effect of interpretations but not that every possible interpretation produces something that, in light of subsequent interpretations, we are obliged to consider as fact … Even should all interpretations be of equal worth, if users can continuously add tags to articles, at some point it is likely that the whole system will become unusable. A folksonomic system threatens to undermine its own usefulness.
Folksonomy advocates seem not to recognize that critical, first decision about retention. The free labor available to create folksonomies is appealing only to those who have already agreed that the entire Internet needs some organization and cataloging.
Since I do not know much about philosophy, I would observe this phenomenon as the philosophical paradigm shift rather than the philosophical problems. Folksonomy would not totally fit into relativism, however, it may need supplemental ground to support (which I honestly have no idea).
However, it should be noted that the author is library-oriented which tentatively support the one cataloger, one object approach. Overall, I think it is an interesting discussion. It may not answer those “then what?” or “why bother?” kind of questions, but at least it could remind us the dichotomous challenges of popularity and professional legitimacy.