[DougWebb]

That pretty much defines a "fad"-based company, doesn't it? I suspect it's very common in the fashion world for companies to pop up, ride a fashion trend, and disappear when it's over, with the founders moving on to start a new company to ride the next trend. Occasionally one of these companies becomes unexpectedly huge, and then they linger much longer than usual. (See: Be-dazzler.)

Maybe that's Facebook's fate. In the end, they'll be a site full of accounts for dead people who, oddly, are still Liking various products and inviting each other to play Farmville.