I usually leave my phone plugged in to the wall charger at night. This morning, to my surprise, the battery was not charged. According to the System Panel app, System Processes were taking almost 10% of CPU during the entire night. The biggest consumer was omap2_mcspi, taking nearly 15 minutes of CPU time, followed by khelper and cpcap_irq/0 both taking around 5 1/2 minutes, then ueventd and used at around 3 1/2 minutes, followed by battd at 3 minutes and vold at 2 1/2 minutes.
It seems pretty ridiculous to me that my battery would be running down while on the charger with the screen off and nothing (that should be) running.
Other than system processes, the only other thing taking any appreciable amount (around 1 minute) of CPU was "usb" which shows up outside of system processes. My best guess is maybe the USB plug had some kind of issue, but I don't see any evidence of this (battery status updates don't show any apparent unplugging).