  We analyze two consequences of the relationship between collinear
factorization and $k_t$-factorization. First, we show that the
$k_t$-factorization gives a fundamental justification for the choice of the
hard scale $Q^2$ done in the collinear factorization. Second, we show that in
the collinear factorization there is an uncertainty on this choice which will
not be reduced by higher orders. This uncertainty is absent within the
$k_t$-factorization formalism.
