  We perform a critical reassessment of the constraints on the R-parity and
baryon number violating (s)top couplings coming from flavor physics. In
particular, we study K0-K0bar mixing, including QCD corrections and a class of
diagrams that were neglected in previous analyses: both effects give sizeable
contributions. We explain how the resulting bounds can be translated into
constraints on individual couplings in the simplest class of flavor models,
based on U(1) horizontal symmetries. We finally discuss the implications for
the possibility of observing single superparticle production at the Tevatron.
