[tatsuke95]

But the 2005 valuations should have accounted for the fact that by 2012 there would be far more internet usage, and priced it in accordingly. In fact, like many things, they could have over-estimated internet usage. I doubt they were saying in 2005, "well, this is all the people who will ever use the internet!"

Anyway, I think the OP here is spot on. It's not that these companies are crap or worthless. It's the size of these valuations. We throw around billions like it's nothing now, when less than 10 years ago it was rare to see valuations 1/10th of that. Name something else that had it's value grow so greatly over such a short period of time. Houses maybe?