The Joker
Thread Killer MKII
Actually it is possible - check out Guru3D's GTX 480 4-way SLI review (about halfway down the page)
I read that article and that's all fine and dandy but if you read the whole article you would note the fact that you need to over clock the cpu by a significant amount to run all 4 cards to there full potential.
The Rig I put together wasn't meant for over clocking, Otherwise I would have stated that.
The CPU will still bottle neck the 4 gpu's.