It's probably not private messages - but it is messages that people think should be private TODAY. But it doesn't really matter - it's perception that matters here. And also I guess this is an illustration of how people's attitudes to FB have changed over time.
"I would NEVER have shared this publicly." they say. But either they did, and now don't trust FB in the way they used to. Or they didn't and there's a bug. Neither are good for FB's brand.
There is no good way to answer "how do we correct a story that was completely wrong," but this seems to be a decent enough way to do it.
That makes me wonder if there is some malicious self-interest behind this. Here's the formula:
ubiquitous yet misunderstood personal technology + sensationalist media + power of suggestion + deliberate astroturfing campaign = sudden and immense drop in stock price.
Not that I actually think this is the case, but it wouldn't be outside the realm of the possible.
1. Take the site down and prevent any further leaks. But accept the absolutely massive flak that would come from that.
or
2. Continue to let the leaking happen and try to hotfix the bug. Be accused of failing to get a handle on it, but perhaps get away with it if fixed in the next 20 minutes.
I'd bet that it's been like this for ages and only just been noticed. That will make fixing it a bit harder I should think - not simply a rollback to the previous push.