The power negotiation alone takes 15 pages in the developer's guide.[1] One can see how an adapter cable with a botched power negotiation protocol could screw this up. Also, statements such as "Should the USB specifications change, then a new firmware will be updated and released" are kind of scary when applied to power negotiation. Especially since you can load new firmware from the connector side of the port. Someone is going to develop an attack based on this, with a USB "power outlet". The OS can't even see this level.

[1] http://www.cypress.com/documentation/application-notes/an965...