Made worse by the video cards being ridiculously fat. As an example, the one I have is two slots wide, and protrudes over the third slot; my motherboard has a PCIe x1 slot there, which is made unusable by that. The fourth and last slot of my motherboard, a PCIe x4, is clearly intended for the Thunderbolt card (there's a special connector near it on the motherboard for the sideband signals), but I can't see much use for Thunderbolt on a tower desktop, so it sits empty.