  We study flavour susceptibilities in the ${\cal N}=4$ SU(N) super Yang-Mills
plasma coupled to two quark flavours at strong coupling and large $N$ by means
of its gravity dual. The off-diagonal susceptibility is 1/N-suppressed and we
compute it as a one-loop effect on the gravity side. Contrary to naive
extrapolation from perturbative results, it attains a finite value in the
infinite-coupling limit. Moreover, its parametric form is independent of
whether or not meson bound states exist in the plasma. We conclude that caution
must be exercised when drawing conclusions about the QCD plasma from lattice
calculations of quark susceptibilities.
