Yet we have regulation because we've seen sellers destroy the environment and take advantage of buyers left and right.
voters in a democracy needn't individually be aiming to elect someone who will be best for everyone's interests
Yet Congress has shone time and again that corruption and cronyism are at it's heart, even if it sacrifices what is good for the people, the economy, or the government. (I don't think the system is even working right now, but that doesn't mean it won't in the future; the US has gone through times lime this before.)
employees of a company needn't all be concerned solely with the company's success
But what happens when employees only focus on their own reward? Companies like that become intolerable places to work at that are hugely inefficient, generally surviving only by cannibalizing itself or by simply leveraging its mass in a pseudo-illegal way). The corporate system is designed for everybody to be doing what is best for the company (which might not always be profits), but that breaks down, too, when everybody starts pursuing their own agenda to the exclusion of anything else.
Systems can take a certain amount of perturbation and survive, but, just like Stuxnet and the centrifuges, if you introduce too much disorder in a system, it will break down. In human society, it seems selfishness, that drive to take care of myself regardless of what it means to anybody else, is often the root cause of that (it certainly is in all the above cases).
It's too bad we can't be a little more communally-oriented (without needing to live in the forest in a VW and not take baths ;). Who wants to do a sun-dance with me to find some extra pollen for the hive?