How do the owners of myspace,facebook etc make millions through the sites?

[xxcsai]

When you have a website that millions and billions of
people frequent, you can easily make money using
services like adbrite, adsense etc. Just by having a
few hundred people click on random ads that they see
on the right hand side of the screen can generate some
good extra cash for you and I. But can you imagine what
millions of page views DAILY would bring in for owners of
fb and myspace? If you can create a site that is popular
and exciting enough to keep people coming back, you can
easily retire early even if you don't charge a membership fee.