In The Story of Stuff, Annie Leonard tells us that all of our "stuff" is part of a linear system that is clashing with our finite planet. Her video is extremely popular (5.5 million views) and easy to follow. Here's a short description from her site:

From its extraction through sale, use and disposal, all the stuff in our lives affects communities at home and abroad, yet most of this is hidden from view. The Story of Stuff is a 20-minute, fast-paced, fact-filled look at the underside of our production and consumption patterns. The Story of Stuff exposes the connections between a huge number of environmental and social issues, and calls us together to create a more sustainable and just world. It'll teach you something, it'll make you laugh, and it just may change the way you look at all the stuff in your life forever.

What are the main problems? We are externalizing costs, so that we are oblivious to the damages we are causing around the world when we buy so much of the stuff that we are buying. We are running out of resources. Her stats from the United States are especially troubling because we are so very much living beyond our means. We generating huge heaps of waste. We are using energy + contaminated products to promulgate toxic products and untested products. One of the highest concentrations of toxic food substances has become human breast milk. 200,000 people move from their resource-exhausted long-time communities into crowded cities, many of them slums. And consider that 99% of the stuff we run through our economic system is trash within 6 months. This is not an accident, either. It is long-time government and industry policy that we should shop and consume. We shop three to four times as much as Europeans. Which, again, leads to disposal problems. For every trash can full of waste we throw away there were 70 trash cans of waste produced to make that one can of waste. Incredible. Many DI related posts can be found here. Further, listen to Daniel Goleman's description of the basic problem and the solution in his interview with Daniel Goleman.