He is referring to the ATX power spec. 12v power for PCIe slots is provided by only two pins in the ATX power connector, rated for 6 amps each. He was pulling 7.4 amps over each pin, which was melting the shroud and likely caused permanent damage to his motherboard. It probably would have started a fire eventually if he hadn't been actively watching it.
His solution was to bypass the ATX plug (and motherboard) entirely by spicing his PCIe extenders to accept power directly from the power supply.
I understand what he did. What I don't understand is why most people are NOT seeing such issues. I have shuffled my cards around quite a bit with my ASUS Rampage III Gene and there is no sign of warping, discoloration or any damage what-so-ever. The slots are never even warm to the touch [or the board if I happen to touch it]. You have to reach down to unclip the card to get it out, so I have little doubt that the board integrity is sound.
Maybe older boards that are closer to spec or lower quality suffer from this issue as opposed to better and newer boards? Like I said, my board gives out a shrill squeal if you attempt to boot with too much power draw [found that out after shuffling cards and forgetting to connect the power to the video card ... when I was experimenting with two cards in my case (answer is too hot and need a larger PSU)]. Even if there is enough power to boot, the board will disable the heavy card [in my case the 6970] when it detects that it can't adequately keep it supplied with sustainable power.
Anyway, it is good to know. I am sure the NVidia 580GTX and 590GTX have similar power consumption [if they know it is there, they will use it].