I've been reading Lords of Finance, which covers the early 1900s. It's eerie how the current situation reflects the pre Black Thursday boom. Investments started to concentrate into a few stocks (then RCA and Montgomery Ward) as retail investors piled in. Folks were buying on margin, credit was easy. The difference now I think is the willingness of the Fed to reduce interest rates to support the stock market as well as a too big too fail ethos. At the time, the Fed wanted to drive out speculators which exacerbated things. I wonder how long the Fed will keep it up.