Comment 23 for bug 936552

It's not really a separate touchpad, it's a /dev/input/mouseX device registered by the mousedev driver for the same touchpad, kind of a legacy mouse device for applications that need that sort of thing. It's there in the good and bad case, and X seems to be (correctly) ignoring it.

I think you may be onto something with the keyboard remove being related. I don't know what's going on, and I don't see it on my MBA 4,1, but dmesg does show usbhid devices disappearing and reappearing about 18 seconds after boot. Actually it looks like the usbhid module is unloaded and reloaded. If I rmmod then insmod usbhid on my machine my touchpad stops working until I restart X.