We flew BA economy back from JFK a couple of days ago and noted this problem. I took care to support the screen or press gently but can imagine the irritation engendered by vigorous prodding. (hold the jokes please).
More of a problem was the large teenager behind who couldn't keep his knees out of my back and the pig next to my wife who made his disappointment at having the empty seat next to him occupied at STD -15 very clear.
Crew were very good, though.
