It won't shock you to hear that the coal industry is facing tough times lately. Job cuts, mine closures and other signs of financial trouble are par for the course. However, that downturn just reached an important milestone: Peabody Energy, the world's largest private coal mining company, has filed for Chapter 11 bankruptcy across most of its US divisions. The firm says it didn't have much choice between steep drops in the price of coal, a weak Chinese market, overproduction of shale gas and "regulatory challenges" (read: better environmental policies). In plainer terms, people just aren't as interested in coal energy as they were in years past.