Great, thanks Robert. After reading your post, I gave it a try myself, and confirmed that an excessive current condition simply causes the musb device to shut down with a lot of vbus errors in dmesg. A reboot of the N800 restores everything to working again.

I should also share a hint about recharging devices like cell phones from a powered USB hub connected to an N800. By default, USB auto-suspend is enabled in OS2008, which causes client devices to be put into suspend mode after two seconds of no activity. Suspend mode is supposed to be low power mode, so most devices won't recharge when suspended. To disable this, change the autosuspend parameter of the usbcore module:

echo 400000 >/sys/module/usbcore/parameters/autosuspend

This changes the autosuspend timeout to 400,000 seconds. This needs to be done before any USB devices are connected.

Keep in mind that disabling auto-suspend will impact your battery life, though, so only disable it when your N800 is connected to AC power! (Or, in my case, a CA-100 cable looped back into the powered hub...)