It’s not surprising to see that News Corp was one of 10 companies given an “F” grade by corporate research firm GMI Ratings for management or accounting practices that could make them risky bets for investors. But Discovery Communications — a Wall Street darling? The GMI Risk List, out today, slams the cable channel owner for having ”a complex system of share classes and director relationships” that give ”two principal shareholders disproportionate control over the company.” GMI adds that  Discovery’s compensation practices “do not hold executives to stringent performance standards.” What’s more, there are “a number of concerns about expense recognition and the quality of the balance sheet, including high levels of goodwill and debt.” Discovery’s stock has risen about 200% over the last three years — a factor Fortune cited last month in naming it one of the “fastest growing companies” —  although it’s off 2.6% in 2011. 

As for News Corp, GMI notes that while there was a “short-term investment impact” in July when the News Of The World phone hacking scandal burst into the open “the company’s share price has rebounded to the level it enjoyed before the scandal broke.” But News Corp’s “poor governance contributed to its recent problems, and may continue to put investors’ interests at risk.”  Despite the resignation of big names including News International CEO Rebekah Brooks and Dow Jones chief Les Hinton — as well as some changes on the board — “there is little indication that the quality of the company’s governance is improving.” For example, GMI notes that “the company’s investigation into the phone-hacking scandal is being led by directors with strong ties to the company and the Murdoch family.” Over the last few days investor advisory firms Institutional Shareholder Services and Glass Lewis made similar criticisms of News Corp, which the company vigorously rejected.

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