It's a real shame that the USB standards creators didn't work harder on error-proofing and longevity.
If I were on the standards committee, I would have made every pin interchangeable - ie. any pin can be gnd, any pin can be Vbus, any pin for data, etc. When plugged in, the device on the end would test every pin, and then decide which to use for data and which to use for power.
That way, when a cable gets a bit old and 3 out of 30 pins are shorted or dirty or otherwise bad, the cable works but simply delivers 90% of the power it used to.
The absolute cheapest cables could have just 2 pins, and would be slow and low power, but still fully 'working'.
This wouldn't have added much cost to most devices either - most devices have a dedicated IC for USB functionality, and that IC can deal with muxing signals and power. On devices which only take power, a simple array of diodes can take power from any pin. Data signals could be capacitively coupled, meaning the muxing could be done on a single chip without needing special high voltage silicon processes (the cost of a chip goes up a lot as soon as you want it to deal with high voltages on any pin).
