  The accurate calculation of weak heavy-to-light form factors is crucial for
the determination of CKM matrix elements from experimental data on B decays. In
SCET, the soft-collinear effective theory, these form factors can, in the heavy
quark limit, be split into a factorisable part that is calculable in
perturbation theory, and a nonfactorisable part that observes certain
spin-symmetries. I discuss the relation between the SCET factorisation formulas
and the heavy quark limit of the corresponding QCD sum rules on the light-cone.
I also analyse the numerical size of factorisable and nonfactorisable parts and
corrections suppressed by powers of the b quark mass.
