A commons problem is a problem of over-exploitation of a resource, or of going along with something because no one really has an individual incentive to act otherwise. For example, fisheries are currently being over-exploited tremendously, because there are no incentives to fishermen to "under"-exploit the fish, because if one of them decides to, other fishermen will just come and catch those fish in the end. So what this fisherman has lost is a chance to support his family. In the end, fisheries collapse, as they are right now. I also think one more reason why commons problems exist is because people feel like they are entitled to whatever it is they are exploiting. It seems as if people feel they have the right to be irresponsible.
How might trash be a commons problem? Well, at least in the US, trash is collected promptly, generally. We don't have to trudge through piles of trash on the streets when you are walking to class. One upshot of this is we really don't know how much trash we are producing. Out of sight, out of mind. But trash is a commons problem in many other parts of the world. The most telling Western example of this is the trash crisis in Napoli, Italy, the birthplace of pizza. In 2008, a trash problem that started in the mid-1990s came into the international spotlight. The landfills in the Campania region of Italy were overfilled, and trash stopped being collected. Convolved with this problem were the mafia and the goverment. You can see the effects of this in this video, which is incredibly shocking, and in pictures here.
Once trash becomes visible, as it did in Napoli, all of the obvious aspects of the commons problem come forth. People continued to throw trash onto the streets. Apparently, more than a million pounds of trash per day were being dumped into the streets. I wonder whether people in Napoli considered fundamentally changed the way they lived and reduced the amount of trash they produced because of it. I would guess not (but I am looking into this), because one extra bag of trash makes very little contribution to the amount of trash being generated.
Let me know if you know anything about this story.