this isn't that surprising. this stuff happens all the time at any company that has that many employees. a person i know who is a software developer at facebook told me that everyone there looks at people's private stuff and reads people's private messages when they want to and you just have to be discrete about it so that no one (i.e. users) notices.
I can tell you that it does NOT typically happen at Google. If you so much as joke about this stuff people will give you negative reactions. I was genuinely shocked to read about this today as I never would have expected any Google employee to be so unethical.
If what you say about the practices at Facebook is even remotely true then it is disgusting and shameful behaviour.
