Well the USB ports have a lot of features that most people do not know about or Nintendo does not tell us or even they do not know. Second the only thing right now that I remember reading was that the USB ports on the back of the Wii could work fine with a portable USB harddrive.

Also the wiimote has a built in microphone

only two of the USB ports are functioning when playing a PS2 game. i guess since the PS2 only had two.

USB ports carry power, and that power can be used by USB devices for charging. Your iPod is one example.

However, if you have an older-generation iPod (the kind that your machine can mount like an HDD), try plugging it in. It reacts very strangely: as though the Wii had mounted it, rather than merely providing power for a charge.