The knowledge management and capabilities literatures are in love — in love with tacit knowledge. Managing tacit knowledge, leveraging tacit knowledge, growing tacit knowledge — these are seen as the keys to achieving sustained competitive advantage.
He's worried that the KM cognoscenti are ignoring other types of knowledge to focus on the tacit. It's interesting to read comments from this perspective, since many KM practitioners think there is too much focus on the explicit.
The thing is that we need both the experience and intuition of the people in the field (tacit) and mechanisms to characterize and record what and how people do things (explicit).
In a follow-up post by Nicolai Foss, What's So Great About Tacit Knowledge? - Cont'd, he suggests that the whole idea of "tacit vs. explicit" is incorrect. That the question should be around how effort is required to articulate the knowledge -- that there is no such things as non-articulable knowledge.