I agree entirely with Henry that blogging can be extremely useful for an young academic career, although perhaps not for exactly the same reasons.
It is certainly true that blogging increases name recognition, and that name recognition is important in all sorts of ways in a job search. Obviously only people who are recognised can be the targets of a targetted search, and a person with a recognised name might stand out of the hundreds of applications in an open search. But I don’t think that’s the most striking way a blog can help. (In philosophy the place the blog could be most useful for that reason is at the immediate post-tenure level, where departments do targetted searches but not everyone knows everyone.)
I’ve never got a job on the basis of blogging, in the sense that I think there’s no offer I got that the blog was the deciding factor in giving me the blog. But having a blog means you get invited to more conferences, invited to give more talks and invited to contribute more papers to collections, and all of these do count towards getting jobs. They count both in that they look good on a CV, and they really start to raise your profile in the profession. So you establish correspondences with prominent figures, something that is also a side-effect of a good blog. (Or at least I’d hope it is. Of course many prominent bloggers already established acquaintances with leading figures in their field at graduate school, but for those of us who studied on the far side of the world, a good blog can go a long way to make up for not establishing a large network in grad school.)
Now regularly corresponding with prominent figures leads to having better letters of recommendation and, if all is going well, better papers. And now we’re talking things that seriously count towards getting a job, and my experience has been that these factors have (I think) made a difference in my career.
Having said all that, this all depends on having the right kind of blog. A blog that is just a record of your sex life is probably not that useful. Or a blog that has too many drunken entries. (My impression was that Ivan Tribble was most concerned with these kinds of blogs to start with.) Even on a purely academic blog, there is some possibility that recording not-worked-out thoughts will lead to a negative impression, especially if the not-worked-out thoughts don’t work out. (Or, again, if the blogger is drunk.) But these cases seem to be in the minority.
And in the long run, there are some things that you should be writing on a blog. I don’t know how much this extends to other disciplines, but a lot of philosophy publication is taken up with papers about why X’s proposal about topic Y is wrong. Now “Philosopher makes mistake” is hardly a headline, so a lot of these papers aren’t surprising. The world would be better off if the journals could be cleared of a lot of them. Of course the good of the world need not be the primary concern of the young academic. (It certainly wasn’t my concern when I was younger, or now for that matter.) Still, there comes a time when it starts to look unfortunate to have all of one’s CV taken up with these little critical notes. (I’ve had to make separate listings on my CV for positive and negative papers just to remove the impression that I do nothing but snip at heels of the more intellectually ambitious.) And at that time you might prefer that those sharp critical comments you’d made had been confined to a well-kept first-rate blog rather than slotted into a second-or-third-rate journal. Certainly the academic world would be better if a lot of these papers were confined to web-self-publication, and after a while their writers will also be better off.
[UPDATE 15/9/05, 2130GMT: Bad typo fixed – thanks for the corrections!]