I know this thread is old, but when using USB hubs, remember that it should be self-powered, not "Buss-powered". the difference is that splitting the signal of a buss-powered hub will usually also split the power supplied to each device. Once the power gets to a certain, critical, low value, the device will usually just stop working. A "self-powered" hub provides its own power (yes, another 'wall-wart') so it does not depend on the computer to provide the extra amperage to any more devices.
In my opinion, this lack of power/voltage and current is just one of the trade-offs made in the development of USB. Low cost, were the first priority, not speed, distance, power, or number of devices. These sacrifices were accepted with the increasing use of mobile, low powered computing devices.