../ in svn:externals?

I see that I can currently set up a svn:externals like this:

../foo svn+ssh://server/path

Or even like this, if .. is not already a svn WC:

.. svn+ssh://server/path

Is this a bug or a feature? I can think of a few off-the-wall uses
(involving keeping ones dotfiles and whole home directory in
subversion), but it seems it could have security implications as well.

-- 
see shy jo