Can social sites turn tons of fans into cash?

SAN FRANCISCO -- It is the burning question in tech circles, and Mike Murphy answers it before it is completed.

"I hear it every time I'm on a (tech) panel," Murphy, Facebook's vice president of media sales, says with a wry smile.

He's referring to the inevitable question on when Facebook and other social-networking sites will turn their steep market valuations into mounds of currency. (Invariably, Murphy answers that Facebook has a long list of major advertisers.)

Facebook, MySpace and other social-networking sites have been the rage of the tech industry for more than a year. Following investments by Microsoft and News Corp., the companies are valued in the billions of dollars and are considered blueprints for how to build a website. Yet a deeper question lingers: How are they going to consistently produce profits to match their soaring valuations?

It is a parlor game that ...