How to fix usbmuxd spam in console when iPhone is connected?
The spam arrived with a recent update to iTunes.  It happens in both Snow Leopard and Lion.  Short of downgrading iTunes versions until the messages go away, there's probably nothing you can do about it.

An update:

The usbmuxd spam only happens when you have a device (iPhone, etc) plugged in and listed in iTunes under 'DEVICES'.  One obvious workaround is to leave your devices unplugged.  A more useful workaround is to just eject them in iTunes – the spam will stop and your devices will continue to charge.