  Only a few molecular clouds in the Solar Neighborhood exhibit the formation
of only low-mass stars. Traditionally, these clouds have been assumed to be
supported against more vigorous collapse by magnetic fields. The existence of
strong magnetic fields in molecular clouds, however, poses serious problems for
the formation of stars and of the clouds themselves. In this {\em Letter}, we
review the three-dimensional structure and kinematics of Taurus --the archetype
of a region forming only low-mass stars-- as well as its orientation within the
Milky way. We conclude that the particularly low star-formation efficiency in
Taurus may naturally be explained by tidal forces from the Galaxy, with no need
for magnetic regulation or stellar feedback.
