Abstract
Assuming factorization, we establish restrictions on BK (K*) form factors imposed by recent data on BJψ+K (K*) decay rates and polarization. We show that these constraints are not satisfied by commonly used models. In addition, we relate BK (K*) form factors to those in DK (K*) transitions using the heavy flavor symmetry as proposed by Isgur and Wise and discuss the uncertainties in this procedure. We find that this method also leads to form factors excluded by data.