It used to be that if you wanted to make use of NVIDIA's multi-GPU SLI solution, you were stuck having to buy a board that was fitted with an nForce chipset. X58 motherboards for Intel's Core i7 CPU changes that.
This is an interesting move for both Intel and NVIDIA. What NVIDIA has done in effect is certify SLI on X58 motherboards despite there being no nForce chipset in sight. Did NVIDIA have a choice? No, not really, not if it wanted hardcore enthusiasts to have access to dual/triple/quad solutions on what will be the fastest CPUs going. Intel gets the best of both worlds and is able to offer enthusiasts both NVIDIA's SLI and ATI's Crossfire multi-GPU solutions for it's next-gen CPUs.
All X58 motherboards will still need NVIDIA certification (which will give them an approval key that can be embedded in the BIOS essential to activate SLI) and vendors will pay NVIDIA a fee for this certification (at present there's no word on what this will be), but it's clear that NVIDIA has now shifted away from the mantra that nForce is necessary for smooth and robust SLI and opening up the platform to non-nForce boards.
NVIDIA also gets to sell silicon to board vendors in the form of the nForce 200 chip that acts as a switch between the Tylersburg southbridge and PCIe x16 lanes.
Intel's happy because it gets the best of both worlds, NVIDIA is happy because it gets to be on board with the fastest CPU going (even if its hand was forced ...), and ATI is happy because it's also not left out of the picture. Oh, and customers are happy because they get to choose their favorite GPU.