Some folks are talking about the Boston Globe article on blogging being essential to a good career.
Between Tim Bray and Jeremiah Owyang I think the list is expanded pretty darn well and the "challenges" of blogging are also touched on. I'd add that another downside is information leakage. Sometimes, personal info you don't intend to share gets inferred, shared, or found and known to others in awkward manners. Not a huge deal given how much better that aspect is understood by folks now a days, but I remember how my friend posted pictures a long time ago that came back to haunt someone else in a job search.
I wonder what Mark Jen thinks of this discussion? He's been on both sides of the fence. He works down the street from me now, and we get together from time to time. I really like him, his peers and the space his company is working on!
FWIW, personally blogging did help me get a job. It also helped get me my master's degree.