A quartz microbalance technique was employed to measure characteristic slip times for ethane and ethylene monolayers adsorbed on silver and chemisorbed oxygen/silver surfaces. These systems have been suggested as model systems for studies of the relative contributions of electronic and phonon processes towards frictional energy losses. Slip times for the chemisorbed oxygen/silver surfaces are observed to be longer than those for silver. Based on this observation, it is argued that electronic contributions to friction should be considered whenever conducting surfaces are involved. Potential connections between the atomic-scale result and macroscopic observation are discussed.