[Catalyst] SubRequest

[apv]

I have a couple of SubRequest questions and forgive me if they're out 
of ignorance/naivete.

Why can only public URIs/actions be used with it? The uses (like page 
includes from TT) that I am interested in trying should not be public. 
I can't think of anything public I'd want to do with it because 
everything that comes to mind, from images/graphs to webservice grabs, 
would only invite abuse if placed outside the context of a site's pages.

Is there a way to tell within the request that it's a subrequest (I 
walked through some Data::Dumper stuff but didn't see anything obvious)?

Thanks!
-Ashley