As far as I know... no tablet can charge via USB. Only the ones with a proprietary plug (ie. Nookcolor) can charge via USB. But its not plugging into a USB port on the device. Odd and convoluted but you get me?
I had a Nook color before my gTab, it was just a standard MicroUSB cable, charged through it just fine. I could charge it on my computer, but not a quick as using the wall charger.