The authors re-examine the transport of momentum in a collisional plasma rotating at sonic speeds. The slowing down rate due to collisional transport is found to be classical ( tau m-1 approximately nu ii rho i2/a2) and the presence of impurities does not change the order of magnitude of this theoretical result. Thus collisional transport theory cannot explain the anomalously high loss rates observed experimentally. Some existing theories of collisional momentum loss are discussed in detail.