Wouldn't the more common use-case for power-hungry usb devices be to have a powered hub to drive them? Then you don't have to worry about browning-out the RPi itself, though of course the cable clutter is worse.
That would be pushing it for powering through just the RPi. Webcams are typically rated for 500mA each and the RPi has been running around 700mA usage. So with the recommended increase, I'd wager their power usage may have gone up to 900+mA.