since jasonharper mentioned that he measured 230ma draw while playing a video, I figured why not try powering it from usb (5V 500ma)
luckily I have a couple PSP usb/charger devices* lying around. and the jack actually fits tolerably well. the juicebox powers up and seems to behave normally. and there is no smell of burning** from computer or juicebox, so I'd say this is a success.
*( http://www.geeks.com/details.asp?invtid=RET-USB2PSP-COMBO and they have a couple other models )
**( for mega usb power and some righteous burning, try this: http://xe.bz/aho/24/ )