Here's my problem:
mint power # uname -a
Linux mint 3.13.0-24-generic #46-Ubuntu SMP Thu Apr 10 19:11:08 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
mint power # pwd
/sys/bus/usb/devices/usb5/5-2/power
mint power # cat autosuspend autosuspend_delay_ms control level persist
1
1000
auto
auto
1
mint power # echo on >level
mint power # echo off >level
bash: echo: write error: Invalid argument
mint power # echo suspend >level
bash: echo: write error: Invalid argument
mint power #
Why can't I power-off the USB device? Clearly the hardware has the capability!