We know that DM interacts gravitationally with ordinary baryonic matter, so we should assume that any DM particles close enough to a black hole will also fall into it, shouldn't we? If so we should assume that black holes must have some DM inside them, perhaps impossible to estimate in which ratio? Many calculations have been done regarding the properties of black holes related to their mass, size surface area etc. Does the "mass" considered in all those calculation include potential contribution by DM in the black hole (it simply doesn't matter whether the mass comes from baryonic matter or from DM)? Or if it does, making all the calculations based on baryonic matter only might not be possibly missing something?