Whenever I boot my computer with the ethernet cable unplugged, the details screen always pops up to point out that it failed to initialize eth0. The reason this bugs me is that I have a laptop. I know it can't start it. I know its not plugged in. Its only a minor annoyance, but is there any way to get it to make a little less noise when eth0 isn't plugged in?
No, you've asked it to initialize the eth0 on boot, and if it doesn't, then it's an error that it needs to warn you about. You could turn off auto-initialization and do it manually when you need it, that's about the only choice you have.