I have a 7-port USB 2.0 hub (this) which comes with external power supply in its packaging. However, when I connected a lot of USB sound cards (Creative SB X-Fi Go Pro! or ASUS Xonar U3) to the hub I noticed it works (every sound card plays or records sound) even without the power supply.
What is the point of the power supply then? Could its absence affect longtime performance (e.g. for server use) of the communication along the USB bus? Is there any difference when using other kind of equipment (such as HDD)?