Ten Reasons Why Blogging is Good For Your Career
I don't know that these reasons would really help somebody decide to start a blog though. Somebody who is interested enough in blogging that he's concerned about his company's policy (whether it has one or not) has better chances starting a blog than somebody who doesn't care but reads Tim's list.
Also, I do see some reasons why it could be bad for your career: if you become a blog addict (can't focus away from your aggregator for more than 10 minutes) or spend your time reading and writing blogs instead of doing actual work. In that view, I see Scoble as an exception ;-)