I vaguely recall a discussion with Bayman about cells being different due to just random fluxuations. A paper in PLOS addresses just that with analysis of mRNA and protein abundance in individual clonal cells. It looks like there indeed is alot of randomness especially when it comes to mRNA abundance (figure suggesting chromatin structure effects above) but it seems (on first glance of the paper) that lots of this effect is buffered and protein abundance is less random. I wonder how OPEN PLoS is and if posting the figure like this is OK?
Summary in Nature Methods (need subscription).