Jim McGee on fostering weblog use within an organiziation:

The management challenge here is a coaching challenge, not a control one. Management needs to encourage you to continue the experiment long enough for you to perceive its value. After a few instances of dumb mistakes avoided by looking back on earlier dumb mistakes and effort saved by referring questioners back to the answer that already exists in the archives, the value ought to be clear. The sharing with others will evolve naturally from better sharing with yourself.

Related to this, if the staff in your organization fear failure then they are not likely to be sharing knowledge effectively (or learning much either). People do not push the limits and try new things when they think they will nailed by management for failing. The trick is not to encourage success alone but to encourage collaborative experimentation with an emphasis on early recognition of failure and why it is occuring.