  We investigate the decoupling limit in the DGP model of gravity by studying
its nonlinear equations of motion. We show that, unlike 4D massive gravity, the
limiting theory does not reduce to a sigma model of a single scalar field:
Non-linear mixing terms of the scalar with a tensor also survive. Because of
these terms physics of DGP is different from that of the scalar sigma model. We
show that the static spherically-symmetric solution of the scalar model found
in hep-th/0404159, is not a solution of the full set of nonlinear equations. As
a consequence of this, the interesting result on hidden superluminality
uncovered recently in the scalar model in hep-th/0602178, is not applicable to
the DGP model of gravity. While the sigma model violates positivity constraints
imposed by analyticity and the Froissart bound, the latter cannot be applied
here because of the long-range tensor interactions that survive in the
decoupling limit. We discuss further the properties of the Schwarzschild
solution that exhibits the gravitational mass-screening phenomenon.
