Robert Scoble, Microsoft blogger extraordinaire, has some useful comments on corporate blogging:
"...what's the challenge for Microsoft and Sun over the next year? Ship great products. Over and over and over. Hints on how to do that are here on the blogs.
This is where blogs will really prove their worth. I'm already seeing it. Teams are now planning on how they'll take feedback on their blogs to improve their products quickly.
I interviewed a team who'll announce a product later this week. They already have a plan so that users can talk back and tell them what needs to be improved. And they have a plan for how they'll take that feedback and put it into action.
(snip)
...That's really where blogs will turn into a competitive weapon over the next 18 months. It's the companies (and groups) who can react to customers that'll really succeed (and be profitable.)"

Scoble is dead right--one of the effective reasons for corporate blogs is to cut the distance between the company and your customers.
Oh and a parting Scoble shot: "The way to learn how to blog is to read 50 blogs in your field for at least two weeks. If that doesn't incite you to blog, nothing will."