My apologies if this has already been covered in this thread, but here goes:
BTW, I should point out that I'm a passnger; a very very frequent flier, but no more than that. Someday I may fly a 'plane, butthat will be my maximum exposure. I am not an expert.
Anyway, to the point: I distinctly remember reading several years ago in the book written by a passenger on the BA flight which ran into volcanic ash over Jakarta that one issue that the passengers had was that when the oxygen masks were deployed they all felt that they weren't working. They expected to feel flow against their face - possibly a cold flow.
I filed that away in my mind for future use if the situation arose.
Is it time to include a mention about how these things work in the emergency briefings? People may assume that its not working and remove them (since they're useles anyway) in order to ask the cabin crew to help them. Foreknowledge might alleviate that situation.