[audunw]

While it's good to avoid EM interference from electronic devices, I think the real reason they want you to switch of these devices is to make sure you're not totally distracted during take-off or landing, and that you're not using headphones, so you'll be aware in case of accidents/emergencies.

[jaywalk]

Nah, they haven't asked passengers to turn off devices in years. They just want them placed on airplane mode so they're not connecting to cellular networks. Bluetooth and WiFi are just fine.