There are bloggers who have achieved some celebrity for their blogging.
And there are those bloggers who had celebrity before they started blogging.
There are a good number of actors like Zach Braff and Alec Baldwin or musicians like John Mayer and others now blogging. Some are using a blog as an on-the-fly website (Braff), or as a component of their main site which is more likely to be maintained by others (Mayer), but some are using it to create a voice that is clearly distinct from their better known celebrity role. The latter is true of Baldwin's blog that is clearly political and not a celebrity marketing tool about when his next film is released. That his blog appears at a blog aggregating site like The Huffington Post, tells you that up front. Still, all celeb bloggers are cognizant of the marketing potential that the medium offers.
We know that in education there is a movement towards having presidents of colleges keep a blog, and having students "officially" blog for their school. And there are those "off the record" blogs that students have that are also "marketing" the school in some ways. The EduWebConference site offers a list of presidents blogging and I'm sure there was/is some trepidation about that idea.
One lesson to be learned comes from Jim Mackey's experience. He is the blogging CEO of Whole Foods. The SEC has recently launched an informal investigation into anonymous Internet postings written by Mackey deriding Wild Oats Market, a company that Whole Foods has been attempting to acquire. This really blew up in his face and as of today his blog is on a temporary "hold."
If you are going to be a celeb blogger, be real. You need to actually do the blogging and make it clear what your intent is in having the blog - blatant self-promotion is OK if you say that up front. No one has to read it. Student blogs designed to show off the best of a school are OK. They might not gain the same following as a "unauthorized" student blog that is more sensationalized, but it has value.
If you are using blogging with your students, it's worth having some discussions about these types of issues.