  We have studied the tunability of the interaction between permanent dipoles
in Bose-Einstein condensates. Based on time-dependent control of the anisotropy
of the dipolar interaction, we show that even the very weak magnetic dipole
coupling in alkali gases can be used to excite collective modes. Furthermore,
we discuss how the effective dipolar coupling in a Bose-Einstein condensate can
be tuned from positive to negative values and even switched off completely by
fast rotation of the orientation of the dipoles.
