Announcements of the WMG–Warner/Chappell deals with Apple‘s iRadio—and rumors of more deals to come—caused Pandora stock to tumble 12% on Monday to $15.06, almost $2 off Friday’s closing price. Apple shares edged up a bit, but the company’s stock has taken a beating lately. Meanwhile, as the likely debut of Apple’s service looms, there’s been speculation in some media circles about possible antitrust issues arising from iRadio. The Washington Post wondered aloud if Apple’s dominance in one area of music, downloads, might give it unfair leverage over competitors in streaming. The Justice Department has accused Apple of price-fixing in the current antitrust trial (over its relationship with book publishers), and Tim Cook was recently hauled before the Senate to explain Cupertino’s tax returns. Still, the paper acknowledges, “Antitrust cases are notoriously difficult for the government to win, at least in the United States,” and the government may not want to meddle in emerging technology markets. [HitsDailyDouble]