At the timestamp of this forum post, the +Options > Edit Meta feature includes both an "Apply to this page" and an "Apply to all pages" button. I've logged in with user accounts that have no admin or moderator privileges, and they can see the "Apply to all pages" button. I feel strongly that this is a significant risk, because a malicious user (or a not-so-malicious user who's not paying attention) could apply metadata to all pages that adversely affects the site.
For example, what if some user intentionally or accidentally applies Robots = noindex to all pages on the site? That would suck mightily. ^.^
At the very least, please remove the "Apply to all pages" button to make it harder for a truly malicious user to wreak mischief. But ideally, you would enable site admins to choose (in the Site Manager) whether to lock out all but admin-level users from being able to see or user the Edit Meta feature.