The real risk factor is necrosis of the breast skin, which is caused by an insufficient blood supply. Remember that original breast skin had say one major blood vessel for every inch of area. As the skin stretches, the number of blood vessels does not increase, so the blood has a longer and longer distance to travel to reach every skin cell. This is the underlying reasons that girls with really big implants often develop really large veins in their breasts, as the body attempts to send more and more blood to supply a larger and larger skin area through a fixed number of blood vessels. Eventually the point of stretching is reached where the skin cells located farthest from the blood vessels simply cannot be supplied with enough blood to sustain them, and these skin cells begin to die. The usual result is that the dead cells form a weak spot in the breast surface, the internal pressure forces the implant to break through the weak spot, infection sets in, and the implants have to be removed.