  Generic Bourbaki ideals were introduced by Simis, Ulrich and Vasconcelos to
study the Cohen-Macaulay property of Rees algebras of modules. In this article
we prove that the same technique can sometimes be used to investigate the
Cohen-Macaulay property of fiber cones of modules and to study the defining
ideal of Rees algebras. This is possible as long as the Rees algebra of a given
module $E$ is a deformation of the Rees algebra of a generic Bourbaki ideal $I$
of $E$. Our main technical result provides a deformation condition that in fact
extends the applicability of generic Bourbaki ideals to situations not covered
by previous work.
