The smartest insight and analysis, from all perspectives, rounded up from around the web: Thirty years ago this week, the U.S. stock market suffered its single most disastrous day, said William Watts at MarketWatch. On Oct. 19, 1987, the Dow Jones industrial average plunged 508 points, or 22.6 percent, spurring "a chaotic, daylong selling frenzy that ricocheted around the world." In today's terms, "a percentage fall of that magnitude would knock more than 5,200 points off the Dow." The Black Monday crash had many causes, but at its heart were overvalued stocks and the market's growing complexity.