Lately I've been working on a lot of automation and monitoring projects, a big part of these projects are taking existing scripts and modifying them to be useful for automation and monitoring tools. One thing I have noticed is sometimes scripts use exit codes and sometimes they don't. It seems like exit codes are easy for poeple to forget, but they are an incredibly important part of any script. Especially if that script is used for the command line.
On System V based OS's the /etc/rc.local file is executed by the init process at the end of the systems boot process. The fact that the rc.local file is executed during the boot process makes it an easy target for misuse by lazy Sysadmins. Since I started my Unix experience on FreeBSD which relies primarily on the /etc/rc.* configuration files, I've seen and shamefully contributed to my fair share of misuse in the rc.