Recent experiments in sliding friction are a major embarassment for all present understanding of friction using Coulomb or Rice-Ruina-Dieterich-Prakash rate-state dependent theories, which are the subject of large research programs. In particular, Rubinstein et al; (Detachment fronts and the onset of dynamic friction. Nature 430, 1005—1009. 2004) suggest that the contact area is not significantly altered by the fast fronts which perhaps are only precursors to the most important "slow fronts" travelling at speeds about 1/10 of the Rayleigh speed.