Attempted hacking does not equal successful hacking
"Every 24 hours 600,000 Facebook accounts are subject to attempted hacking or violation, Facebook has revealed."
so 600,000 times per day Facebook detects someone trying to do something malicious. That is not to day that 600,000 times a day an account is hacked.
So this is pretty much useless information, as this is the stuff they are aware of. The stuff to worry about is the successful attempts which they are not aware of.
I am not defending Facebook here, but this is like saying "Would be thieves try the handles on 100,000 cars per day". So yeah, hackers may be rattling the handles and testing the locks, but that's not a successful hack in my book.
and 600,000 a day doesn't sound a lot for a site like facebook. Large sites like that will be a magnet for attempted hacking. A simple dictionary attack could account for a good few 100,000 attempts easily.