Well in all seriousness you probably were not in *that* much danger. Sounds like the cabin was not keeping pressure and was slowly depressurizing as you climbed. Then once the cabin pressure droped below a certain level the O2 masks automatically deployed. Just shows the safety systems were working and really the whole situation was probably not that big of a deal.
A slightly more dangerous situation would be a rapid depressurization at altitude. Even this is well trained for by airline crews. Above certain altitudes the pilots are required to have o2 masks at the ready and are also trained to do rapid decent techniques to get to a safe altitude in minutes. Assuming its a minor leak, and not a giant hole in the side of the fues sucking people out, chances are again in this situation you are really not in that much danger. Being at 20-30,000 feet isn't really that bad for you for short periods of time. You might go hypoxic and even pass out but if you get down in a reasonable amount of time there is little chance for long term damage. Chances are you'd get the o2 mask on before any of that happened anyway. I have paragliding and hang gliding friends that have flown to 23,000 with no o2, not the smartest thing (or legal) but it can be done. PG pilots have been sucked up in clouds to even higher alts and survived to tell the story.
I've been in a plane when the o2 masks drop. I admit for the first moment it startled me too and all kinds of things raced through my head, probably not from the masks dropping but from half the plane screaming at once. But after a few seconds it was obvious it was either a malfunction or the cabin only had a slight pressure problem, and we were not in real danger. It was funny to look around at some of the expressions of peoples face for the next few minutes though!
