One question that came up in conversations during the Great Ideas Conference was, "Can a blog be outsourced?" Sure, much like any other communications vehicle. If you were to do that, I would suggest that you work with someone who is familiar with blogging, and make a definite plan for the type of content to be used and how often it's going to be updated.
But remember, blogging lends itself to immediacy and a conversational tone that will require your attention as well. It's important that the blogger you hire understand your organization, industry/profession, and culture.
Blogger Jeremy Wright, who made news a few weeks ago by auctioning his services on eBay, wrote a good piece on "why companies should hire bloggers" that is worth a read.