Intriguing and fun piece on some well-known Brits who may or may not really be on Fb.
BBC NEWS | Technology | Are my online friends for real?
Same can be said about any form of online communication but the notion of a “Facebook bug” which Stephen Fry may have caught is more specific than the Fb-hype we keep reading.
Disparate 
Fake faces would probably not matter so much, IMHO, because the pictures have little to do with whether or not a SNS entry seems genuine.
Just wait until morphing technology begins to look real and then all the social networks are at risk of “fake faces”.