 Why are neighboring genes co-expressed at the RNA level? While it is tempting to think that this is to enable coordination of functionally related proteins, analysis of human proteomics data by Rapsilber and colleagues, Custature et al, suggests this is the exception not the rule. Rather it might either be just something that happens or, in some instances, an epiphenomenon of coordination of expression to enable reduced gene expression noise. This article was authored by Lawrence D. Hurst.