Here's a few linkes to blog posts on corporate blogging:
Enterprises Begin To Embrace Web 2.0 by Ron Condon, CIO Today
"According to Jorge Lopez, industry research chief at Gartner, the focus of I.T. has been to cut costs by automating tasks that can be broken down into discrete processes. But it has achieved all it can in that respect and any further improvements would be marginal. The next frontier for I.T. is the non-routine work that lends itself less readily to automation -- and here the talk is of augmentation: helping people come to decisions more quickly, and helping support any consequent action. "
"'With knowledge workers, such as managers, who deal with non-routine kinds of work, the idea of productivity is different. As [management guru Peter] Drucker pointed out, you don't pay them by the hour but by results," says Lopez. "The question is: how do you help that class of worker become productive?'"
In the post "Measuring Social Media And Corporate Blogging", John Cass lists a number of potential goals for corporate blogs, including a list of possible measures for quantifying if you are successful or not.