From an interview with Anil Dash, SixApart honcho, lover of purple:

I think we’ve seen a number of huge benefits companies get from business blogging. Having blogs means companies can communicate better: between employees, workgroups, project teams, or different locations. Or between a company and its partners or customers.

It’s a cheaper way to share information, a powerful way to collect feedback, and a faster way to respond to the conversations around its products or services. It’s also a much better channel for marketing communications than traditional PR, if your target audience is regular people.