USB 3 changes that somewhat - high- and low-speed operations can run simultaneously: http://en.wikipedia.org/wiki/USB_3.0#Architecture_and_features

As for pass-through ports, depending on the type they may not be electrical at all. For example, a VGA device could plug into the VGA port using special screws that can't be easily removed. A lock would be attached to the device, thereby securing the computer. The device itself would just have to lead the VGA pins out to a new, offset connector. It wouldn't need to use any electrical power or signalling from the VGA port.

http://targus.com/ca/drivers_manuals_archive.asp?SKU=PA492C

>With USB hubs all devices run at the speed of the slowest device. Do pass-through ports work the same way?
>
>>I think some if not most of the devices that plug into "popular ports" are pass-through i.e. you can continue to use the ports, they just get extended some distance outward. Like the old parallel port dongles used for copy protection.
>>
>>Some more ideas at http://superuser.com/questions/555373/ways-to-physically-secure-laptop-that-has-no-kensington-lock .