After 10 years of production, shale gas in the United States cannot be considered commercially viable, according to scientists. They argue that while the use of hydraulic fracturing and horizontal drilling for "tight oil" is an important contributor to U.S. energy supply, it is not going to result in long-term sustainable production or allow the U.S. to become a net oil exporter.

Source: Scientists wary of shale oil and gas as U.S. energy salvation