The reason you see more pros than cons is because you haven't put the time into finding/learning about the cons.
You and everyone who thinks Facebook allowed them to reconnect with long lost "friends" and family. *EEZZZZZ* Wrong.

You got this ability just by having the power of the internet at your fingertips. And you think that it's FB that gave you this but it's because it's the first social forum you've tried. There's are millions of forums on the internet with infinitely more value. For personal connections, if they're worth it, you'll find them through one of the many valuable messengers that existed for years/decades. Or maybe visit them in person?

Everyone has to stop thanking FB for this. Where's all this love that should be for email that has openly helped many more people connect and communicate for decades? Email is 100x more valuable than FB wishes it could be. And it's based on open protocols/code. Which is something that FB is not. You're not even limited to a single platform. You can talk to any email address out there!