Getting this short:

Can current flow from a powered USB hub's power adapter (lying 10 Meter away) back to computer via usb port and cause damage to Computer components like mobo, etc? What should be my concerns?

Using a 2 Amp 5V Power adapter to power a 10m Long Active Repeater USB extension cable with 4 port HUB & plugging into PC's Front port, causes

• PC Chassis fan to keep running (thought slower than regular speed)
• Front Chassis HDD & power LED to turn on (though bit dim)
• may be other things which i cant detect/see at chip level, in motherboard?? All this even after PC is shut down (bit scary)

More detail (in case still want to read):

To run 4 High power (needing >450 mAmps) Wifi Adapters, far away from PC, Bought Active Repeater USB Extension Cable with 4 Ports & power port at far end http://www.ebay.com/itm/33FT-USB-2-0-Male-to-Female-Extension-Cable-Hub-Splitter-Adapter-with-4-USB-Port-/390846115254

Then added a locally bought 2 Amp 240V AC to 5V DC Power Adapter and plugged into USB hub which is a part of & situated at far end of a 10 Meter Active Repeater usb extension cable.

Even 4 Wifi Adapters run fine (appear to) using this setup, but running chassis fan, dimly lighted Power & HDD LED, even when PC is switched off is bit scary and surely mean 5V & some current is flowing all though that 10 meter extension cable into my USB port & powering stuff.

Can this cause damage? and what should be my concerns. Of course I can't switch off the power adapter (lying 10 meters away from PC) every time I switch off my PC to prevent this.