I’m not sure it’s all right, but a provocative piece about Facebook & co. at the excellent Knowledge@Wharton site, with lots of quotes from Kevin Werbach, who usually is right. The implication is that they will become the victims of their own success, expand too far, and the digital natives will leave them for the Next Hot Thing.

The short study says: “Underneath Facebook’s expansion plans is a conundrum facing any social networking site: How do these companies expand into new markets without losing what originally made the site popular and alienating their existing customers? For instance, if a site starts out as a trendy online hangout for young people and then begins courting senior citizens, it is unlikely its initial customer base will stick around, say experts at Wharton.

“Couple that dilemma with the fact that social sites’ business models are already fragile, and a loss of focus could be fatal.”