Most of the cases I've seen (and that would be hundreds) used for porn DVDs have hubs made up of four high-pressure prongs. The stress caused by these prongs may ultimately cause the two polycarbonate layers to separate, leading to "DVD rot." I came across one such instance recently, which resulted in no playback at all from the disc. Aside from creating stress on the disc, the hub's sharp edges also have the potential to damage the DVD as it is being attached or released. The attached disc should be able to rotate freely; it shouldn't be rigid. I'd be willing to pay extra for a decent case, like the Amaray cases many mainstream movie studios use.