  A critical examination of the spin dynamics in high-$T_C$ cuprates is made on
the light of inelastic neutron scattering results obtained by different groups.
Recent neutron data show that incommensurate magnetic peaks in YBCO belong to
the same excitation as the resonance peak observed at $(\pi/a,\pi/a)$. Being
only observed in the superconducting state, the incommensurability is then
rather difficult to reconcile with a stripe picture. We also discuss the link
between the resonance peak spectral weight and the superconducting condensation
energy.
