You felt pretty pleased with yourself for jumping on the latest Ubuntu release back in the alpha stages on your virtual machine, then having it running on your laptop and Lynn's Asus EEE 701 the day after the final release came out.
But did you ever have to change the default runlevel? NO, you didn't. You didn't anticipate that you would want to convert that alpha-6 server into a workstation. Nice thinking, hero. And now that you've figured it out, you're going to remind yourself that the place to change it is in /etc/init/rc-sysinit.conf. You might want to look at the env DEFAULT_RUNLEVEL setting. Oh sure, you could manually create an old-school /etc/inittab file, and it would get picked up from there. But, you know, throwing away a grand old tradition like that really feels liberating, doesn't it?
So now you know. Don't forget, okay? But if you do, you might just find yourself coming back here.