  Electroweak baryogenesis is a simple and attractive candidate mechanism for
generating the observed baryon asymmetry in the Universe. Its viability is
sometimes investigated in terms of an effective field theory of the Standard
Model involving higher dimension operators. We investigate the validity of such
an effective field theory approach to the problem of identifying electroweak
phase transitions strong enough for electroweak baryogenesis to be successful.
We identify and discuss some pitfalls of this approach due to the modest
hierarchy between mass scales of heavy degrees or freedom and the Higgs, and
the possibility of dimensionful couplings violating the decoupling between
light and heavy degrees of freedom.
