  Motivated by the results of an experiment using atomic force microscopy
performed by Gotsmann and Fuchs [Phys. Rev. Lett. {\bf 86}, 2597 (2001)], where
a strong energy loss due to the tip-sample interaction was measured, we
investigate the potential implications of this energy loss channel to the
quality factor of suspended micro- and nanoresonators. Because the observed
tip-sample dissipation remains without a satisfactory theoretical explanation,
two phenomenological models are proposed to generalize the experimental
observations. A minimal phenomenological model simply extends for larger
separations the range of validity of the power law found experimentally for the
damping coefficient. A more elaborate phenomenological model assumes that the
noncontact friction is a consequence of the Casimir force acting between the
closely spaced surfaces. Both models provide quantitative results for the
noncontact friction between any two objects which are then used to estimate the
energy loss for suspended bar micro- and nanoresonators. Its is concluded that
the energy loss due to the unknown mechanism has the potential to seriously
restrict the quality factor of both micro- and nanoresonators.
