As the overall stock market experienced another plunge in its recent roller-coaster ride, some investors in media stocks hung on for dear life Thursday. The Dow Jones U.S. Broadcasting & Entertainment Total Stock Market Index fell 4 percent, but media companies that rely the most heavily on advertising revenue plunged far more deeply. For a time shares in CBS Corp. were down nearly 15 percent on Thursday before recovering somewhat in late trading and ending the day down 9.8 percent to $22.48. But even conglomerates less exposed to possible retreats by advertisers were hammered hard. Cablevision dropped 8.0 percent to $17.17 percent; Time Warner, 6.2 percent to $28.59; News Corp, 5.3 percent to $16.31; Viacom, 5.0 percent to $41.47. Two media companies that appeared to steer clear of the volatility were Disney, which slipped just 2.5 percent to $32.55 and Lionsgate, which remained unchanged at $7.13 (possibly because of reports that maverick investor Carl Icahn was buying up more of its stock for another possible takeover attempt). Still, some analysts suggested that investors were displaying undue apprehension. Benjamin Swinburne of Morgan Stanley reiterated his forecast for 3.2 percent growth in the media industry this year and 4.1 percent next year. He predicted substantial increases in corporate advertising budgets over the next 12-18 months. Young and Rubicom CEO David Sable told the Financial Times that networks that sell much of their ads during the so-called upfront just-passed season are in the best position to weather any approaching storm. However, he acknowledged, "The volatility in the stock market may have caused some overreaction, and that ... could affect advertising" particularly at the local level. David Hallerman, an analyst at eMarketer, also cited the strong upfront season as a buffer against any emergent economic decline. "The numbers are set and locked in," he told the FT , "so if we see ongoing cutbacks [in advertising], the results will be in 2012."