...so says Tim Bray:

1. You have to get noticed to get promoted.
2. You have to get noticed to get hired.
3. It really impresses people when you say “Oh, I’ve written about that, just google for XXX and I’m on the top page” or “Oh, just google my name.”
4. No matter how great you are, your career depends on communicating. The way to get better at anything, including communication, is by practicing. Blogging is good practice.