In the center of a black hole sits it's singularity. An infinitely dense point. I question, because this singularity is said to be infinitely dense, then shouldn't it's mass be infinite as well. Well this cannot be so, seeing that gravity is based on mass and distance, and we are not currently being sucked into a black hole. But imagine that this black hole does have infinite mass. We could expect that distance between us and black holes would regulate this much gravity, but even lessening infinity is impossible. Thus, there would have to be some sort of energy or force that regulates this gravity and keeps it at bay. SOmething that breaks the laws of physics that we know of. Howhever this is all speculation, seeing that we will never know the explaination of "infinite" density until we venture into a black hole.