Hugh McLeod's got a super useful post on corporate blogs, corporate blogging and how those pesyk PR and marketing departments can embrace their inner transparencies. Apparently, this is a talk he gave at Edelman PR--and I hope they tattoed the words on their inner arms (okay, I hope they listened closely).
Some of what stood out for me:

• The growth will come, I believe, not by yet more increased efficiencies, but by humanification.
• If corporate blogs work, it's because they help humanify the company.
• Blogging is not about reaching a mass audience.
• Blogs allow you to cheaply and quickly begin a smarter conversation.
• Having a "Smarter Conversation" is not an intellectual decision. It's a moral decision.

There's lots more and it is a great read with case studies, links, and references.