We review the mechanical properties of defective roughened surfaces with the major emphasison nanoindentation work. We also report novel results in which force versus penetration curvesand AFM images of the nanoindented surface are compared for a flat surface of Au(001) and anAr+ bombarded one, both with a high and a low flux of ions. We have found that bombardedsurfaces yield at a lower stress than untreated flat ones. Surfaces bombarded at high fluxshow a large roughness and their yield point, marking the onset of surface plasticity,decreases with respect to that of the flat surface or of the surface bombarded with a lowflux. The present results are compared with earlier work on nanoindented vicinal surfacesin which the sole surface modifications with respect to the flat surface were thepresence of a high density of steps. It is concluded that a softening effect dueto the bombardment-induced nanostructure of the surface dominates over thehardening one due to defect creation and interaction in the surface neighbourhood.