Taking photos/videos of the flight experience, don't know if it's generally accepted, but I'd

1. Avoid any other person in frame;
2. If crowded, avoid their faces;
3. For meal distribution where the cabin crew is in, I'd avoid their faces into frame; and not to publish their direct faces;
4. Use a small camera/phone to not make a scene;
5. Make my camera visible so others know I'm filming (and filming what);
6. Be available to show and remove any image involving another person once requested.

Re suction cup thing, I do film takeoff on camera handheld (airplane mode; admit I'm not strict safety guy), and I'd understand the claim that the suction cup might loosen and fell during the takeoff/landing vibration.