Wait there is a button that controls every's life? And if a crew forgets, its game over for all?
The cockpit is literally filled with switches and knobs that could kill you if they're set incorrectly and warnings are ignored and/or don't work. That's why pilots go through years of training, have years of experience before they're allowed in a commercial cockpit and have checklists to make sure they set everything correctly.
Cabin pressure is a checklist item: http://www.b737.org.uk/nnp.htm
Scroll down, it's "pressurization mode selector" set to AUTO.
There is a warning horn if the cabin altitude rises above a certain number (though I'm not sure what that altitude actually is).
We don't know the full story here, and may never because it's not a story the media's likely to stay on top of. But at this point it's just as likely that some mechanical problem developed and the pilots *did* react to it, descending the plane once they received the cabin altitude warning, as it is that they "forgot" to set the selector correctly. Nobody died here and the pilots remained in control, unlike, say, the Helios accident. That suggests to me that the plane (or at least the cabin altitude) never got high enough to cause hypoxia.
I'm tired of being a wanna-be league bowler. I wanna be a league bowler!