According to theory, virtual particles appear in pairs of opposite charge and quickly destroy each other when they collide. But when they appear on the edge of a black hole so that one particle is on each side of the event horizon, one particle is sucked into the hole and the other remains in normal space.

That brings up a couple of other questions then.

Does a black hole prefer one type of charged particle versus another?

And, if you entangle a group of atoms and send half of them into the black whole then won't information be transmitted out of the hole when something happens to the atoms that are in it? Since they're entangled, what happens to one set should immediately happen to the other. If the event horizon doesn't break up the entanglement then that brings up another question - do the atoms outside the hole age at the same rate as those inside the hole, or do they age at different rates?