Always interest to see what the formal policy is when one of these discussion occur, found this on the united site by searching on "photography" -- highlighted colors are mine.
UA policy on
Onboard photography and video policy
United Airlines strives to make its customer experience safe and comfortable and accordingly has issued the following policy in regard to the use of personal audio and video equipment onboard its aircraft. This policy is not a contract and does not create any legal rights or obligations.
Customers who bring personal audio and video equipment onboard may only use these items with headsets. Noise-canceling headsets may be activated. The use of still and video cameras, film or digital, including any cellular or other devices that have this capability, is permitted only for recording of personal events. However, photography, audio, or video recording of other customers without their express prior consent is strictly prohibited. Also, unauthorized photography, audio, or video recording of airline personnel, aircraft equipment, or procedures is always prohibited. Any voice, audio, video, or other photography (motion or still), recording, or transmission while on any United Airlines aircraft is strictly prohibited, except to the extent specifically permitted by United Airlines.
also see this blog
Is Photography Prohibited on an Airplane?