Facebook has your address book, so they have the phone numbers and names of all of your friends, work colleagues, family members and other people you happen to know. They can see your entire social graph. This kind of metadata is extremely valuable. If you just have the phone number of someone in your phone book who at some point becomes a terrorist, you are now also under full investigation. I don't know about you, I find this scary and dystopian, but unfortunately it's real. If someone you know does something that's wrong, you are now also a suspected criminal. Metadata is sometimes even more valuable than the actual data itself. To quote the former NSA director Michael Hayden: "We Kill People Based on Metadata". Especially since the Snowden leaks we know that we should protect ourselves from corporate/government overreach and surveillance and the best way to do this is avoiding proprietary software. FOSS is superior in any way: It's built by voluntary individuals who just want to help out other people and try to make the world a better place, it's transparent to the user and can be verified, you have the freedom to do with it whatever you want. We really shouldn't be supporting multi-billion dollar corporations lead by weirdos. Did you know that Mark Zuckerberg bought all the land around his house, so that none of his neighbors can see what he is doing for privacy reasons, while he probably caused the biggest invasion of privacy in the last decade? We shouldn't be supporting such people. We really shouldn't.