Build a “business blogging platform” that includes approval levels. Basically it would work the same way that any approval levels for spending happens in companies. Some people can’t spend anything, some can spend a bit, and some can spend A LOT.
Every time an employee posts to your business blog an approval chain is kicked off where one (or multiple levels) of management have to approve the post.
I’m not suggesting this as a way that startups should blog – but maybe it would make big businesses more comfortable with blogging. Build a blogging platform that allows corporations to vet information, and we may find that we have more Fortune 500 bloggers.