[turbo6bar]

Like the other posters, I believe bubbles are fueled by greed and underestimated/ignored risk.

As far as a trigger, I don't think one could nail down a nexus. Multiple conditions could set up a bubble.

I can see how the peons (the citizens) could be fooled by the last bubble, but how did the financial big-heads fall for the trap? Were they looking for perfect profits without due diligence? Were they assuming risk was zero? This reminds me of a proverb about bankers. I don't remember the exact wording, but it was: A banker who shuns risk and keeps his bank afloat isn't admired. A banker who takes risk, maintains pace with his competitors, and fails, isn't punished. That banker was merely going with the crowd. Sad, isn't it?