The Great Depression in the US followed a period of economic centralization and "prosperity" at the top, of relaxing of financial regulations and controls, and gross mismanagement similar in structure though smaller in scale to the economic conditions we are seeing now.  The one great difference was that the GD was a collapse of the banking system only--the physical infrastructure remained intact and the US was able to recover with its strong industrial base.  So while the signs of a banking collapse are present now, the means for recovery are not.  

Even so, food was a problem as farmers destoyed food that people needed but had no money to buy.  

After the Second World War food was again a problem in Europe--at least on the continent.  

By the end of the Second World War nuclear weapons were invented, and were soon extensively deployed.  The possibility of civilization ending through nuclear war has remained with us ever since.  This is new, even if--since the end of the Cold War--the odds seem small, and the effect on people's sense of well-being is deep.  Flying saucers make their public appearance about this time--and without weighing in on that subject--I will venture that the public attention is connected to underlying unease.  I would propose this same unease underlies the public response to disaster predictions you cite.  I might add that now that Bush is promoting nuclear war (those "bunker busters") against Iran, the world can hardly be said to be in good hands.  

In short, recent history gives us no reason to think that people will behave well, or that things will always be fine.  

Of course, the things I described were merely shattering, "civilization" did continue, even if the changes did render one age largely incomprehensible to another.  (And it did--go back and read stuff written before WWI:  The atmosphere of prevailing thought is nearly inaccessible.)  

Let's look at religious trends:  In the 19th century a new fundamentalist Christianity was invented that saw the apocalyptic gospels of the Bible as applying to the immediate future.  Though based on wrong scholarship and bogus interpretation, and despite being proved wrong on particulars several times, this apparently crazy version of Christianity gained adherents in the US to the point where at the turn of the 21st century it is a major political force.  One of the odd things about this fundamentalism is that adherents believe as Christians that they should do the devil's work to advance God's timetable for bringing the end of the world about.  As a practical matter, they support policies of environmental destruction and political disruption that interfere with long-range human survival, deliberately.  

Lastly, geology is rather against us.  Peak oil may be a new topic of public discourse, but the issue has been with us as a practical matter for 35 years, and as a theoretical one longer than that.  There were things that could have been done to prepare--on the scale of an entire civilization--but they weren't, and now arithmetic is not in our favor, in the sense that the civilization we have been living in simply cannot continue, and therefore won't.  I cited Cuba to show that mass-die off is at least theoretically avoidable, but that said, the future can look nothing like the present.  

A newer wrinkle in geology is climate change, which has been a theoretical issue as long as peak oil, but which has shown up as a proven problem in only about the last decade.  As climate changes it will disrupt the biosphere and make human survival more difficult.  How difficult?  The folk of sub-Saharan Africa are already fated to die, as the desert expands south.  As for the rest of us--there is really no way to tell how bad it will be.  Where I live now will be under water before the century is out.

Is a bang better than a whimper?  A good question.  We are currently in a race between malign technologies and the undermining of the support infrastructure for those technologies.  Which will win?  What the US government has planned in the way of surveillance certainly makes Stalin's police state seem an amateur effort, but whether they will be able to implement their fantasies is far from sure.  Similarly in biology and biological control.  Politically, the age of independent science is just about over, increasingly, new discoveries are going to be paid for and applied to strategies of domination.  This is, fortunately, self-limiting, but the whimper scenerio implies a longer period of truly amazing agony.  Also, the longer the process takes, the greater the destruction to the biosphere--we are already on the boundary of the greated die-off of species since the end of the dinosaurs--the more prolonged, the starker the boundary will be.  That a large die-off means more opportunities for new species, is a good thing if you are alive to enjoy them a million years from now.  

So certainly a crash seems better.  Except.  To traverse the crash well takes preparation, and that needs time.  

A standard optimization problem with contradictory constraints.  

The Fates are kind.