Hi. I have an usb optical mouse, and when i shutdown my computer, the sensor light stays on.
I believe usb is powered because even my gamepad got his little led on. I don't want this because i don't want to use un-necessary power and i like mice and don't want them to die young.
I had this problem before, when i enabled power on with any keys in my bios. Then i selected the keyboard only on and my mouse was off at power down.
Some day ago, my PC was off and i realized the mouse was on, so i totally desactivated power on keys but the mouse stayed on. Then i recompiled my kernel with ACPI and i got no more success. I re-recompiled with APM, and the mouse stayed on.
I believe this is a Linux shutdown "issue" because i know there's PC off and PC off. I experienced that with the wake-on-lan when i realized the ethernet card can be on after a shutdown.
I searched around without success, so here i am, requesting your help, Linux users from earth!

I do not think this is a linux problem, I think it is a motherboard / BIOS problem.
I have the same with an ASUS P4S800 MoBo, the mouse light stays on whatever I do to the BIOS, so I turn it off at the wall now.

Exactly right, it would do this under windows, too. Some motherboards actually have otpions int he BIOS to turn this "feature" on and off. usually it is called USB Idle Status, or USB on poweroff, etc. Should be either in the Advanced options or onboard peripheral section of your BIOS.(assuming it is there) If not, if you powered it down anyways, just unplug the machine, or the USB devices, or just hit the power switch on the Power Supply so none of the machine gets power. However, I highly doubt a mouse's life will be shortened by having power, it is like an LED, even constantly on, it could run for decades with no ill effects.

If it was a bios setting, then my mouse should have been off forever when the PC is off, because it used to and i didn't change any bios setting.