Life as a public company has been bumpy for Pandora: the slightest leak about Apple’s upcoming iRadio service makes its share price dive, for example. Now there’s a new factor: fears over a slowdown for the mobile advertising market. Pandora’s stock price fell 5.9% to $12.12 yesterday based not on its own financial figures, but on those of mobile advertising network Millennial Media. Billboard explains that Millennial reported less-than-stellar financial results of its own and lowered its guidance for the first quarter of this year – spooking investors who saw this as a bad sign for Pandora, which made nearly 62% of its revenues from in the final quarter of 2012. At a time when mobile advertising is high in the minds of music industry execs – and reportedly streaming services like Spotify too – the performance of Millennial and its rival mobile ad networks will be scrutinised carefully in the coming months.