I was having a discussion recently regarding the fact that *nix doesn't use things like a registry (in the Windows sense) and how this means that everything related to an application (or anything for that matter) sits directly in the filesystem.
This got me thinking: if I wanted to backup an application install, is snapshotting the appropriate directories sufficient? The purpose here would be to allow me to wreck havoc on an application knowing that I can quickly roll back to a known good state.