In Social Software: Knowledge Management Redux? Mike Gotta draws the connection between knowledge management and social software that I have seen as well. Here are some key sentences trimmed out of the full piece (go have a read):
One area where KM has garnered success has been in the area of community-building (e.g., communities of practice). ... A consistent theme behind social software is to take advantage of informal interaction and make it purposeful by facilitating group connections based on common attributes (e.g., interests, activities, location and information) that are explicit or inferred. ... [T]he unforeseen discovery of peers doing similar things that result in purposeful action as a derivative outcome of informal interaction across small groups, larger communities and loosely-coupled networks makes social software quite consistent with KM goals.
If KM is about anything, it is smoothing bumps in the path of finding, using and creating knowledge. What better place to do this than within human interaction? I also like his opening brief on the travails of knowledge management as a concept.