Question: Is there a way to have a RewriteRule fire on any domain that is requested on a box? For example, I have 5 VirtualHosts that would have the exact same RewriteRule applied to them and currently each VirtualHost directive has the rule, but can I put this somewhere 'global' so that upkeep is easier?

Answer: 
No, I'm afraid not
I haven't tested it, but the [mod\_rewrite docs](http://httpd.apache.org/docs/2.2/mod/mod_rewrite.html) say that RewriteRule can be used in the server config context.

You may also want to look up how [RewriteMap](http://httpd.apache.org/docs/2.2/mod/mod_rewrite.html#rewritemap)s work. Since these are a file, they could be considered to be a "global" source, but there are limitations on them since they are primarily static.