  This paper is concerned with the long wavelength instabilities (infrared
catastrophes) occurring in Bose-Einstein condensates (BECs). We examine the
modulational instability in ``cigar-shaped'' (1D) attractive BECs and the
transverse instability of dark solitons in ``pancake'' (2D) repulsive BECs. We
suggest mechanisms, and give explicit estimates, on how to ``engineer'' the
trapping conditions of the condensate to avoid such instabilities: the main
result being that a tight enough trapping potential suppresses the
instabilities present in the homogeneous limit. We compare the obtained
estimates with numerical results and we highlight the relevant regimes of
dynamical behavior.
