Somebody please help me understand

...why Facebook is considered to be worth $42 billion?

Facebook's latest valuation, according to trading on SharesPost Inc., an online marketplace that trades in shares of private companies, is greater than that for Internet giants EBay Inc. or Yahoo Inc.

"Over the years people have paid premiums for the companies best positioned for long-term growth and margin expansion. For good reason, Facebook is perceived of as one of those companies," Standard & Poor's analyst Scott Kessler said. "Whether or not at this point in its life cycle it deserves to demand a valuation that essentially makes it the second- or third-most valuable Internet company on the planet is an open question."

I understand that companies use Facebook as an advertising site, a way to hook up with potential and current customers. Writers, musicians, etc use it as a way to connect with fans and promote themselves. A lot of people use Facebook. Is that what makes it worth $42 billion? Has anyone tried to estimate total business earnings as a result of presence on Facebook, assuming that's even possible?

So far, I have friended/fanned pages of some companies I already have done business with. Sometimes I click through newspaper or magazine links that interest me. Is that where the worth comes in?

Somebody please help me understand

...why Facebook is considered to be worth $42 billion?

Facebook's latest valuation, according to trading on SharesPost Inc., an online marketplace that trades in shares of private companies, is greater than that for Internet giants EBay Inc. or Yahoo Inc.

"Over the years people have paid premiums for the companies best positioned for long-term growth and margin expansion. For good reason, Facebook is perceived of as one of those companies," Standard & Poor's analyst Scott Kessler said. "Whether or not at this point in its life cycle it deserves to demand a valuation that essentially makes it the second- or third-most valuable Internet company on the planet is an open question."

I understand that companies use Facebook as an advertising site, a way to hook up with potential and current customers. Writers, musicians, etc use it as a way to connect with fans and promote themselves. A lot of people use Facebook. Is that what makes it worth $42 billion? Has anyone tried to estimate total business earnings as a result of presence on Facebook, assuming that's even possible?

So far, I have friended/fanned pages of some companies I already have done business with. Sometimes I click through newspaper or magazine links that interest me. Is that where the worth comes in?