Why do websites like Youtube and Facebook for so much money?

[Craig M]

What revenue does it generate? I can see some ads here and there on Facebook but after that what else? I rarely see ads hosted by the site if any on youtube. What gives? Tehy both sold for BIG moola!
My only reasoning is those ads are that expensive?

[apeskape]

If they are bought out for millions they most likely generate a couple million per year. This is because they have millions of visitors that generates alot of income from advertisements.