Screaming Penguin

I am using a spammy title for this because there are a number of similar issues. HOWEVER, if you leave your Android phone plugged into your your Mac with USB debugging, particularly if you are using a MacBook Air (MBA) USB ethernet card, the "kernel_task" will runaway on you. Especially if you are streaming Flash video or anything that spams the network card. Unplug your phone or turn off the USB debugging in the developer settings.