The median person still thought that their prices were going to go up. That's the definition of a bubble.
"Richard H. Thaler" is an USA/American economics/economist and the Ralph and Dorothy Keller Distinguished Service Professor of Behavioral Science and Economics at the University of Chicago Booth School of Business. He is perhaps best known as a theorist in behavioral finance, and for his collaboration with Daniel Kahneman and others in further defining that field.More Richard Thaler on Wikipedia.
At the moment no one can prove that these Internet stocks are overpriced. But many of us have deep suspicions.
There is no doubt that these are real people making real choices for high stakes, and we rarely get to observe such pure decisions.