> You might say - and I'd certainly agree - that the real problem is a world where everyone is on Twitter and Facebook to the exclusion of all else

Then I would say you are living in artificial world delightful for advertisers. I have a Twitter account that I have not really used in a decade and nobody else in my family has ever touched Twitter. My wife has a Facebook account she uses to keep in touch with family, but nobody else in my family has a Facebook account. I know MANY people in my professional world who have neither.