For the record:
I don't have specific info on this incident in hand, but this is clearly a 'high-dive.' Delta confirmed it. A 'high dive' is a rapid (safe) descent to 10,000 feet--an altitude where almost everyone can breath safely and without undue stress. It's not a normal maneuver and unless you've experienced it first hand, you have no idea what it's like--unless you're had some other types of flying.
When airliners are in cruise (at altitude, say 39,000 feet), if the cabin pressure can't be maintained (leaky hose, broken duct etc...) the aircraft MUST descend to an altitude that will support all the passengers on board easily. Why did I say this? Old, young, infant, impaired folks may not be able to tolerate exposure to high altitudes/low oxygen for any significant period of time. Additionally, a rapid change in pressure (explosive or just 'rapid') is also bad. Finally, the maximum altitude that the cabin is exposed to is what determines the severity of the situation and the need for medical attention.
So?
If you rapidly descend (safe but maybe uncomfortable), you may minimize the exposure and prevent the oxygen masks from dropping and avoid the need to have medical care/examination/distress for ANY of the passengers. By all accounts, the Delta crew did a fantastic job and avoided an unsafe situation with professionalism and calm. Note the flight attendant calmly walking through the cabin helping folks and keeping them safe. Nice job Delta.
Funny, people laugh, joke, talk, watch TV, listen to music and generally IGNORE the safety briefs.
Not funny, when the oxygen masks drop from the ceiling, people panic and realize 'life is fragile.'
Maybe we should pay more attention?