We study the dependence of the heat transfer and the van der Waals friction between two semi-infinite solids on the dielectric properties of the bodies. We show that the heat transfer and van der Waals friction at short separation between the solids may increase by many orders of magnitude when the surfaces are covered by adsorbates, or can support low-frequency surface plasmons. In this case the heat transfer and van der Waals friction are determined by resonant photon tunneling between adsorbate vibrational modes, or surface plasmon modes. The enhancement of the van der Waals friction is especially large when in the adsorbed layer there is an acoustic branch for the vibrations parallel to the surface like in the case of Cs adsorption on Cu(1 0 0) surface. In this case we show that even for separation d = 10 nm, the van der Waals friction induced by adsorbates can be so large that it can be measured with the present state-of-the-art equipment. The van der Waals friction is characterized by a strong distance dependence (∼1/ d6), and at small distances it can be much larger than the electrostatic friction observed in [B.C. Stipe, H.J. Mamin, T.D. Stowe, T.W. Kenny, D. Rugar, Phys. Rev. Lett. 87 (2001) 096801].