No one is accusing Dr Kovac and his colleagues of the sort of sharp practice for which Dr Obokata was censured. Instead, the argument is about whether their results were really solid enough to justify the rapturous reception they were given, says Katherine Mack, an astrophysicist at the University of Melbourne. But both cases reflect the rise of open, post-publication review on Facebook and Twitter, by e-mail, on blogs, and in the comments sections of websites like arXiv, which hosts preprints of papers in physics and mathematics. As Paul Knoepfler, a biologist at the University of California, Davis, whose blog was used to co-ordinate the efforts of those trying to replicate Dr Obokata’s work, puts it, “I suspect that if published even five years ago, the [stem cell] papers’ serious problems would have gone unnoticed for far longer.”