EMI on a plane is no joking matter:
Found a few reports in a Lufthansa Technical bulletin describing instances of EMI effects on aircrafts avionics: In one case a cheap CD-Walkman in business-class caused the Autopilot computer to display erratic course and speed settings on a 737. More spectacular was the effect of a WLAN enabled laptop (the WLAN module was even deactivated but obviously still pumping out RF signals) which made the autopilot throttle down the engines on a Airbus 340... thankfully this was while cruising and not at a critical flight stage like take-off or landing. Also common are GameBoys causing flight management computers to display an error message in the cockpit. On the other hand during a maintenance test flight, the engineers fired up a cell phone directly in the cockpit and placed a call without problems. They tried that even in the avionics bay, again without any effects on the plane.
Nevertheless, there are a whole load of reports such as these so it is no joke when airlines say turn off the gadgets, especially in TO or LNDG, ignoring this can place you and all the other passengers and crew at unneccesary risk.
Besides, I would think it would be pretty hard to receive a radio station while sitting in what effectively is a faraday-cage travelling at 700 - 900 KpH, or am I wrong at that?