I think half of the members in this thread should apply at AMD for an VGA engineering job.
Geezus. You know that some motherboards offer Crossfire or SLI up to 4 slots? And those slots DONT even have an extra Molex-connector? How do you think these boards will hold up the moment you put 4 cards in without any PCI-express booster? That's 4x 75W's pulling from PCI-E bus alone, over 2 wires on that poor 24 ATX connector.
Geezus people even many ancient motherboards offer onboard Molex-connector, it proberly sits near the PCI-express slot which feeds an additional current.
And if it's not there, you'd buy a pci-express booster:
This way you are able to pull more current then the standard 75W's.