The Natural Gas Supply Association (NGSA) recently released a study of price transparency in the U.S. natural gas market, finding that it is "arguably the most price transparent commodity market in the world."
An examination of the interaction between the physical and financial U.S. natural gas markets shows that there is enough transparency. In fact, the combination of transparency on both the physical and financial sides of the market makes the overall market close to being completely transparent.
A copy of the report, as well as the related NGSA press release, can be found here.