While I don’t use a professional proofreader for my blogging, I do use one for nearly all other writing, including copy for clients, articles, and books.
When a proofreader is not someone you use, then you lose.
Example: a digest mailing from Preston James promises the reader will learn about a special web site on page 73.
But the digest is only 71 pages long!
Once a large accounting firm had me in to train their managers in writing. “Be sure to emphasize proofreading,” the client told me. Why? The cover of a proposal to a major account referred to the firm as “certified pubic accountants.”