But greed and stupidity are "natural" forces at work within the capitalist system. Asserting that crises are cyclical and "naturally emergent" doesn't rule out greed and stupidity as causes. It actually doesn't say anything about causes at all.
I'd also be wary of concluding that because certain phenomena appear to be cyclical, any similar phenomena must necessarily be an expression of that cycle.
I think it's very hard for people to see bubbles as forces of nature, because in retrospect you can always see how dumb they were. So it always seems as though, if we just rationalize the system a bit, then we'll no longer have bubbles. However, no system has yet been invented which is capable of preserving rationality within a modern economic system. Hundreds of years of evidence suggest that whatever reforms are attempted as a result of this crisis will eventually run into the same mishaps and errors as ever before, unless someone comes up with a truly systematic account of bubbles.
You're right that I shouldn't assume that this crisis is an expression of cyclical booms and busts. I'm very puzzled by this crisis, and the information that's available is maddeningly vague and handwaving.
Actually it is even more general than that. The pattern of exponential growth followed by die-off is common throughout nature - algal blooms, for example.
It seems that the whole discussion over the financial crisis has been warped and twisted by this absurd belief, in the face of all evidence, that the economy is in some sense "rational," that it has some kind of steady-state equilibrium, and that its problems are therefore caused by too little or too much regulation, too little or too much greed, etc.