The Hausdorff distance, the Gromov-Hausdorff, the Frechet and the natural pseudo-distances are instances of dissimilarity measures widely used in shape comparison. We show that they share the property of being defined as $inf_rho F(rho)$ where $F$ is a suitable functional and $rho$ varies in a set of correspondences containing the set of homeomorphisms. Our main result states that the set of homeomorphisms cannot be enlarged to a metric space $mathcal{K}$, in such a way that the composition in $mathcal{K}$ (extending the composition of homeomorphisms) passes to the limit and, at the same time, $mathcal{K}$ is compact.