I don't agree that "microsoft already does this" - so don't take what I'm about to say to mean that. I mean only to show a piece of technology that more directly relates to the comments others have made.
That being said, Microsoft has developed a piece of technology called PhotoDNA[0], which is designed with the specific purpose of identifying child pornography. This is actively used on OneDrive and Bing, among other services - including Facebook. It's safe to say that OneDrive does not just delete the content if child pornography is detected - it reports to the authorities. Now, it's hard to argue that they don't have a right to do that, as long as the person is voluntarily using their services. That's where I draw a distinction here: Facebook could elect to turn on PhotoDNA on photos uploaded to their new service, and not properly educate their customers that stuff is being uploaded automatically. This does, essentially, constitute a passive surveillance system. Mind you, if it is used to establish that child pornography is found, you will have a hard time convincing most people that it is overstepping what Facebook should do. That's my concern - that this will be pushed as a "for the children" thing, and then extended to "to cut down on crime" later, once everyone stops caring about its existence.
That said, that's my concern. It's not necessarily what I think will happen. I have no reason as of yet to believe that it's the next step. I do not, however, want Facebook automatically uploading (or even scanning) my photos.
That article mentions both Microsoft and Google, and closes with "In addition, the software is used by Facebook and Twitter, among others." (referring to PhotoDNA to scan all your pictures in all your mails - only Google's and Microsoft's reaction to matches is described in the article though, I guess we can infer that Twitter and Facebook would do the same).
Sounds interesting. Source please?