There's a proximate vs. root cause argument going on here. In 87 and '00, the stock market was absolutely overvalued relative to historical metrics like the ones linked (and in '08 the real estate market was). It is today too. Now, the proximate causes were not "overvalued" because ultimately something has to "happen" to push an unstable system into a correction.

But realistically the corrections were inbound regardless of the specifics about automated trading, the startup economy, or bank solvency.

There's one coming "soon" now, too. Eventually.