There are a lot of news articles about this, but I figured this crowd would appreciate The Colbert Report's coverage. Basically, there was a very popular study that found that, when countries exceed a public debt to GDP ratio of 90%, their economic growth becomes negative. A graduate student, Thomas Herndon, when tasked with duplicating the results of this study, found that he couldn't. The original study contained coding errors in its excel spreadsheet. In fact, the average economic growth for countries whose public debt to GDP ratio exceeds 90% is 2.2%, not -0.1%.
This is very significant. The original study was used to justify austerity measures in Europe, and Republicans like Paul Ryan have been referencing this study to justify dramatic and immediate cuts in the federal budget. After the study came out, Nobel Prize winning economist Paul Kreugman pointed out that the results of the study couldn't be replicated, but now we've found the specific reason as to why.
Ideally this would put an end to Republican deficit-hawking so that we could actually concentrate on stimulating economic growth, but of course, if conservatives cared about science there would be substantially fewer conservatives.