The Globe and Mail reports in its Thursday edition that Sears Holdings Corp. investors on Wednesday got news that there is "substantial doubt" that the retailer can continue as a going concern. The Globe's David Milstead writes that while Sears is its own special basket case, the real meaning of the news is to underscore the perilous nature of investing not only in retail, but also in real estate, something the smart money has already figured out. And even though the carnage is concentrated in the United States, Canadians should take note about what it means here. Bloomberg reported earlier this month that Wall Street has found its next big short in U.S. shopping malls. A growing group of hedge funds and other investors are shorting securities backed by the commercial loans taken out by the operators of shopping malls and strip centres. Canadians should be warned, in particular the holders of RioCan, which exited the U.S. in 2015, and any of the REITs that stick to domestic ownership -- whether via one retailer such as Loblaw or Canadian Tire, or the more diversified ones. This is a slow-motion tragedy that could easily head north, and there is no telling how much retail we will need in a fully digital world.