At 100 million visitors, $25M translates to $4 a month per user in ad funds. $4, per user, per month, sustained for 24 months. Just to break even.
Those are insane prices at insane growth trajectories. You can call that justification of a valuation, but I call it unsustainable speculation.
The people who believed Google would monetize their business in a huge way seemed to do alright. I don't think Murdoch regrets his decision. I do think people should be cautious but you're going way beyond saying just that.
The money being talked about though for Facebook and others cannot possibly be recovered though unless a number of stars align, and that's too much for me. ;-)
Still think it's crazy?
He's projecting 60% ish growth.
Unless I'm misunderstanding what you are trying to say, you're off by an order of magnitude:
$25M/100M = $0.25
Maybe it's not so insane after all.