USB3 is supposed to support up to 900 mA, while USB2 (and 1) was 500 mA. This is just the spec and not how much a given device can or will draw.
Now I'm kind of wondering the power draw of most USB-powered devices. If a port can support a 2.5" external hard drive—consider the power drawn by the motor spinning up, the heads—surely it can support a DAC that doesn't even include an integrated headphone amp. These should be some reasonably low-power electronics that the ODAC has. I mean, CEntrance DACport has a DAC, a DC-DC boost converter or two (and something for the negative rail too), and a class A headphone amp. That's a USB-powered device too. Something seems off to me.
Edited by mikeaj - 8/27/12 at 8:58am