I have a question regarding this... I bought snow leopard family pack & made a bootable copy onto a USB flash drive. I have been able to reformat my MBP & MacBook in various occasions, by just powering while holding the option key (it brings me the options to boot from the USB flash drive or the normal HD.
Now I bought a new MBA 11" and I tried using my USB flash drive to reinstall the os (delete all the extra languages, printer drivers, junk gathering space), but whenni tried booting from the flash drive, the MBA would go grey screen of death and i would have to restart the computer. As soon as I plugged in the little USB reformatting device that came with the air, it went ahead with no hiccups. I know that you can't use the MBA thumb drive on other macs, but I didn't know that you can't use other USB drives to boot the air. Has anyone gone thru the same thing?