The 5v USB can spin the Intercooler's fans, but it won't spin fast though. They are 12v fans, and if they're not spinning fast enough, I think it will bottleneck the hot air pushed out by the internal fans, and that might not be good...

Anyways, I was worried about the Intercooler problems, so I've done some sawing, and chopped off the power section of my Intercooler. I'm sealing up the big hole soon, and adding a switch and a molex. It will draw power from my computer PSU, since that's usually on when I'm on the xbox. Right now it's powering 2x 9cm intake fans at the right side of the xbox, and I've had no overheating issues.

You still have to get around how to plug the power in. Many intercooler problems are due to power sapping of the 12V mains, but there have been cases of short-circuits and socket meltdowns from the intercooler power socket. I just chopped off the power socket part.