Trying to decide how serious this is.
I mean, it is quite plain to see that Linkedin is integrated into the 365 world (I switched that off earlier). But by default, this largely just seems to connect your email inbox to people's registered LinkedIn account profile pic, name and job title (unless you then go onwards to connect, whereby you can get some notifications in the e-mail contact window).
Facebook integration... I mean that is more serious. Is it now? (imagine CEO's sharing email contacts - and I'm sure the US never spy on content huh?).
I can see that there is an option in older Outlook to decide to integrate Facebook. Probably using the Facebook Graph API. Sounds like a shit idea.
It also claims the process is that Facebook graph API would send Microsoft the contact details, not the other way around (I am open minded to it going both ways). It also claims Microsoft had to roll back access to various elements of this API in 2015...