Not really a knock against AMD. Back in that day, I was very much an AMD (CPU) fanboy... the reason I went with the 680i was because CPU-wise, intel's Core 2 was indeed better, but intel's own chipsets were so same-y and limited, and for lack of better wording, boring. nForce chipsets were undisputably king for AMD CPU's because they were indeed faster and all the OC records at the time were done on them (DFI boards most frequently). But then, as if hearing the cries of those having to contemplate a platform switch, NVIDIA just came out of nowhere and brought us a chipset for those Core 2 CPU's that just blew the doors off what intel itself was offering at the time.
It wasn't until the first-gen i7 that intel even bothered to offer SLI support for their chipsets; and fewer boards made that actually had the lanes and slots to support it. So it was annoying, but not surprising, when intel just started suing or refusing to renew licences for the likes of SiS, ULi, et al to make supporting chipsets for intel CPU's. All I could surmise on the AMD side, is that when AMD (the CPU company) bought ATI (the GPU guys), several people saw the writing on the wall, feared the same behavior, and NVIDIA (among others) just didn't bother.