Here's the part of interest for those not interested in the full article:
"U.O. took more than two years to design, and, according to Koster, who joined the development team in 1995, a great deal of that time went into trying to perfect what was known as the "resource system." Under this system, both natural and man-made objects were coded according to the imaginary resources that went into them—a sheep, for example, was a couple of units of meat and a couple of units of wool—and the total pool of each resource was fixed, so that there would always be a certain amount of meat in the world and a certain amount of wool. One of the goals of the system was to produce a naturalistic and therefore dynamic environment: the sheep would get eaten by wolves, and as the wolf population grew the sheep would decline.
Under the resource system, players could gather raw materials, like ore, and make them into finished goods, like armor, which, once used, would begin to break down and reënter the pool as raw materials. Players, it turned out, liked to make things—they were turning out hundreds, and even thousands, of swords and shields and gauntlets—but instead of using them, or throwing them out, which would have had the same effect, they hoarded them. One player reportedly had a collection of ten thousand identical shirts. The result was that there were hardly any materials available to replenish the pool, which deepened the environmental crisis.
At first, the design team tried to deal with the situation by funnelling in more resources, but these, too, were quickly grabbed and hoarded. No one could figure out how to keep the game going without giving up on the system: in the virtual world, as in the real one, economic growth and ecological stability can be tragically difficult to reconcile.
Now the game is programmed so that the servers continually add more ore and sheep and wolves to the landscape. This largesse has solved the mass-extinction problem, but not the hoarding, which continues, contributing to server lag. Why players hold on to so many essentially useless items remains a mystery. When I asked Koster about it, he said, "Why do you have all the junk you have?"