The interaction between the tip of a near-field scanning optical microscope (NSOM) and the sample it scans is analyzed and compared to a simple tapping model. The approach curves acquired with the NSOM are in excellent agreement with the model, and additional experiments strongly point against a noncontact interaction (such as shear force). Based on this model we are also able to explain the oscillations pattern of the feedback loop. We conclude that our straight-fiber tip, operating under “shear-force” control, intermittently contacts the surface it is scanning, in a way similar to the tapping mode in atomic force microscope.