I thought I'd give this an extra thread to make it stand out. It's on the cohorts issue. For those that don't know, the CDC used its empiric criteria (Reeves et al., 2005) in the negative Switzer XMRV study in Retrovirology. There's a petition against it at: http://www.ipetitions.com/petition/empirical_defn_and_cfs_research/ with some links to other information and critiques of the criteria. These criteria have also been used in other "dodgy" CFS research e.g. the two CDC studies that linked CFS to childhood abuse.