Access callback for user blog pages.
function blog_page_user_access($account) {
// The visitor must be able to access the site's content.
// For a blog to 'exist' the user must either be able to
// create new blog entries, or it must have existing posts.
return $account->uid && user_access('access content') && (user_access('create blog content', $account) || _blog_post_exists($account));
}