One of the things I really like about Linux is the availability of source code for the kernel and userland applications. If I encounter an issue where a program is misbehaving for some given reason, I can grab a source RPM from a network repository and start poking around to see what is going on. Fedora and CentOS provide the yumdownloader utility to download binary RPMs, and source RPMs when the "--source" option is specified:
$ yumdownloader --source kernel
Loaded plugins: refresh-packagekit
Enabling updates-source repository
Enabling fedora-source repository
kernel-2.6.31-0.17.rc0.git15.fc12.src.rpm | 67 MB 05:28
Once a source RPM is downloaded, you can install it and begin looking through the source. Sweet!