Mr. Frank McDonald:

The problem in any bubble is the perception that the only way to go is up. The warning seen at the end of some advertisements for financial products which says "Markets may go down as well as up" was forgotten during the boom. Developers forgot it, too. A massively overpriced asset did not seem massively overpriced to them at the time because they were all caught up in this belief that everything was onwards and upwards. That was the risk.