Reminds me of the all-hands meeting Microsoft had a few years ago concerning security flaws.
On the other hand, Facebook's recent privacy changes have (presumably) come from the top. So if they call an all-hands meeting, it seems like it can only be to either say "we've changed our minds", or "the public are wrong, and we won't change our minds". I can't see much of an actionable outcome for FB staff, unlike after the MS meeting.