Christian Crumlish write a too-brief post on tags as collecting behaviour and says:
Tagging and other forms of collecting are also an example of social design patterns that mimic game dynamics. Collecting objects is a core "easy fun" activity in many games, and similarly these extremely lightweight social interactions around gathering or tagging objects enable a form of self-interested behavior that creates aggregate value and potentially richer forms of engagement.
Tagging is one of those incredibly flexible ideas that can be implemented in a multitude of ways and contexts. What innovative uses of tagging and collecting behavoiurs in enterprise are you witnessing?