Stardate 20010822.0919 (On Screen): There's a paradox in economics called
the tragedy of the commons. It's the counter to Adam Smith's contention that an economy will act optimally if everyone in the economy works to their own self interest. The classic example is a common grazing area. There is only so much vegetation there, and if it is overgrazed then it will grow back less rapidly and reduce the vegetation available in future. Continued overutilization of the common grazing area will destroy it, leaving nothing at all. So it is in the best interests of the community as a whole that the overall rate of grazing be limited to a level which sustains the grazing area while maximizing the grazing on a continuous basis. Exceeding that level will cause a temporary increase in food for the animals but a long term decline. The problem is that if everyone complies with the restrictions except one person, he benefits more than anyone else. There's an incentive to cheat. He gets to raise more animals, and the damage caused by only one person overgrazing is minimal and probably not even noticeable in the grand scheme of things. So each individual reasons that he'll be the only one who defects (the technical term for this) and the commons won't be damaged. Unfortunately, since a lot of people do reason this way, the result is substantial overgrazing and destruction of the commons, to the detriment of everyone.
This is in fact actually happening in a lot of places where there is shared grazing, especially in the US in places like Nevada and Wyoming. But it's more apparent in the world's fisheries, which are now in serious crisis in many places. A fisherman has an incentive to catch as many fish as he can, to make money to feed his children. (The person who defects isn't necessarily evil or greedy; he may just be poor or desperate.) As a result, fishermen collectively have been exceeding allowable catches and fishing in restricted waters for a long time, and many of the world's great fisheries have collapsed. In some cases conditions permit very strong governmental control (i.e. over salmon fishing in the Columbia river) but when the fisheries are in international waters it can be very difficult to police.
Modern medicine is subject to the tragedy of the commons. There are a lot of people who are quite willing to accept a blood transfusion in an emergency to save their lives, who at the same time are not willing themselves to donate blood. If too much of this happens, then those of us who do donate cannot maintain the supply and there may not be enough. That is indeed becoming a danger now. Organ transplantation is another such issue where the tragedy of the commons has already happened. There are far more people who need organ transplants than there are organs available, and hundreds of people die every year who could have been saved. I think that the only real solution to this would be a law which said that no person can be given an organ transplant unless they are either a minor or have themselves been a registered organ donor for at least five years. Absent that, we're probably going to continue to have a shortage of transplantable organs for the forseeable future. It's probably going to get worse, in fact, as the technology of transplation continues to mature.
Vaccination is 
a modern miracle; indeed it is the modern medical miracle. Of all public health measures, it has saved more lives than any other except for the establishment of modern water supply and sewer systems. But though vaccines can prevent terrible diseases, they are not perfectly safe and there is a very small chance of them causing harm. For instance, the Sabin polio vaccine has largely eliminated polio in the industrialized world. But the Sabin vaccine consists of live polio viruses which have been weakened so that they cannot create disease. There is an extremely small chance that the weakened virus can mutate and return to its normal form, and since the Sabin vaccine became available and went into common use, this has in fact happened one or two times in the US. By comparison to the hundreds or thousands of people who were horribly crippled by polio, this is obviously a good trade. The vaccine has other small risks associated with it, some of which haven't actually been proved. (Some think it has a small chance of inducing autoimmune disorders, for instance.)
But there's something known as "herd immunity". What it means is that if everyone in the world is vaccinated against polio except my children, then they are capable of getting the disease but won't because they won't ever be exposed to it. They are protected by the fact that everyone else has been vaccinated. But it also means that everyone else has taken that small but nonzero risk associated with the vaccine and my children have not. When the risk of polio seems slight, the risk from the vaccine itself looms large (because of a form of fallacious reasoning called
