"It's not what you know, it's who you know?" 

Agree or disagree, but there's no doubt a key capability of a law firm's KM initiative—assuming you actually want your attorneys to use it—is some capability for finding the apposite expert who can help.  I've called this the "Ask Sally" moment, as in, "Ask Sally; she'll know."

Within a law firm, a simple exercise in "Social Network Analysis" (SNA) can map who really is talking with who, and the results often surprise a firm, for better and worse.  A very common experience, for example, is to find a few very highly connected individuals appearing as hubs of knowledge exchange:  The problem is that many of those networkers extraordinaire are actually bottlenecks, suffering overload, as the sheer volume of incoming (and they're usually incoming) requests for assistance impairs their ability to get their own work done with a modicum of productivity.   Unless you try SNA, you may never know.

I've discussed SNA before, but now CIO magazine has nice story including a sidebar about how Orrick is playing with it.   Can you say, "timely?:"

"[T]he corporate world has been waking up to the uses for this once arcane social science. Some of the interest stems from disappointment with efforts to build knowledge management databases that were largely ignored by employees. "We're seeing that companies want to have a picture of who the key knowledge brokers are in their organization," says [Prof. Rob Cross, of UVA's McIntire business school]. "The rise of blogs, online support sites and social networking sites—such as Friendster and LinkedIn—have also helped raise SNA's profile."

I've been reading Prof. Cross's 2004 book, The Hidden Power of Social Networks, as he seems to be the go-to guy for SNA.  Look for a review in the near future.