I used to work there a while (5 years) ago, and I don't think you understand how this company works. There are internal groups where features are discussed and

I used to work there a while (5 years) ago, and I don't think you understand how this company works. There are internal groups where features are discussed and debated all the time, and even all hands Q&A sessions with Zuck (weekly IIRC) where sometimes hard questions are raised. Someone amongst the many engineers with access to the repo will eventually end up spotting shady code if it exists. They might raise this with a colleague first, or in an internal group, and the matter might even bubble up to the Zuck Q&A if it's intentional and particularly controversial. This level of internal openness is unusual at this company size, and since there are people joining & leaving all the time (including interns who AFAIK have the same level of access to the code) it would take just ONE disgruntled whistleblower to ignite a scandal that the press will be instantly all over like piranhas smelling blood, this being Facebook. Therefore, doing evil covertly like you suggest just isn't worth the risk for FB, period. Not happening, won't happen. When you see headlines like "Is Facebook eavesdropping on phone conversations?", Occam's razor is always your best friend.