The Tragedy of the Commons (summary)
Hardin's paper has been highly influential, although that doesn't mean that everyone has agreed with everything he wrote. The journal Science has links both to the original article and to commentary published in the same journal.
Here are what I see as Hardin's three main points:
1) some problems can't be solved through better technology, but require a change in human behavior;
2) freedom for individuals to pursue their own self-interest in ways that seem harmless, individually, can collectively result in conditions that hurt everyone -- if I graze two cows rather than one on the village commons, I'll have twice as much milk to sell, and one more cow won't hurt the grass, but if everyone grazes two cows, the grass will be so badly damaged all the cows will starve;
3) freedom for individuals to choose how many children to have is an example of #2 (population will grow enough to undermine human well-being) and #1 (better technology can't solve all the problems resulting from over-population).
I plan to discuss each of these points in this blog, probably (like most previous commentators) paying most attention to #2.