My great insight during the Great Housing Bubble was that I knew that not nearly enough people had nearly enough money to afford those mortgages. I did not need my Ph.D in economics to tell me this, I just exist in this world and knew it to be true. Early on I didn't know about all the crazy securitization so I didn't know it was going to blow everything up, but I knew people's incomes couldn't support those prices. Because incomes are a quaint outdated concept.
As investors stop buying up houses we'll probably have another bubble popping in some regions. No jobs, no money, no mortgage payments.