The stock market's torrid rally has left it vastly overvalued and vulnerable to a horrific plunge, says Henry Blodget, editor-in-chief of Business Insider. "Every valid valuation measure I look at suggests that stocks are at least 40 percent overvalued," he writes on the service. Among examples Blodget cites is that the cyclically adjusted price-earnings ratio, based on 10 years of profits, stands at 25, compared with a long-term average of 15. In addition, the current ratio of stock market capitalization to revenue is 1.6, compared with a long-term average of 1.0, he notes. And the ratio of stock market capitalization...