First, let me apologize for bringing a zombie thread like this back from the dead. But I know I read quite a few outdated threads myself on the basis of search results. So allow me a moment to comment upon this one.
I was told that the UBS port would NOT provide voltage unless a device asked for power. I bought this story at first, and later decided it had to be bull####. A device needs power to run, to tell the port that it's been plugged in.
My specific experiment was to build my own USB light for my Audrey. They sell them at stores for about 20 bucks. But you are looking at a light bulb, a USB cable, and a coat hanger. That to me is not worth 20 bucks. So I went into my garage, gathered the junk, and built my own. Works great.
While the USB port may be very limited in usage for the Audrey, it does indeed supply a very steady supply of 5 volts. Remember though, that like a woman, Audrey is delicate and sensative. Abusing her for your power may not be a good idea. There are a lot of 5v power supplies out there.