Amazon appears untouchable. It’s rallied 37 percent this year, outperforming the market nearly fourfold. And a stunning quarter, reported last month, prompted nearly two dozen firms to up their price targets on the e-commerce giant; a handful of those newly minted price targets place the company north of the $1 trillion threshold.But at this juncture, I suspect a black swan has taken flight. Just consider the stock’s presence in so many passive vehicles. Amazon is a top holding in over 140 exchange-traded funds. A liquidity event for Amazon shares — perhaps triggered by issues related to the Trump administration’s ordered review of the company’s impact on the U.S. Postal Service — would create uncontrollable selling, in our view. Zooming in further, around 40 ETFs hold Amazon within the top 5 percent. Look out below: This is a colossal failure of common sense. Investors have been stuffing themselves on a Thanksgiving feast full of technology stocks. Today, tech sector equities comprise nearly 30 percent of all large-cap mutual fund portfolios; this is an accident waiting to happen. This represents the largest “overweight” relative to traditional benchmarks, relative to other large-cap sectors, in two decades. This represents, too, nothing more than a passive overdose on big tech, setting up large downside risk. This development causes me to hearken back a decade. Of course, who could possibly forget the great gorging on the financial sector heading into the crisis? Leading into 2007, banks and insurance companies comprised nearly 24 percent of the S&P 500. Today, the tech sector’s large market weighing puts it up near 26 percent of the market’s total capitalization.