Morgan Stanley analysts on Wednesday downgraded their rating on shares of Zillow Group on news that the real-estate media company would ramp up its home-selling initiative. "We appreciate the option value" in this venture, the analysts wrote, "but see it as lower quality and riskier." Zillow shares have already gained 20% for the year to date, the analysts wrote, "and risk/reward now appears balanced." What's more, the new push into what's often called "i-buying" "have emboldened short sellers," in part because the venture is lower-margin. "We expect 2018 to be volatile and lower our price target to $50," from $55, they added. That's essentially flat compared to Wednesday trading levels. By comparison, the S&P 500 index is up 1.5% so far this year.