at fsfla.org we still use a single SVN server with different subdirs for the public web site (ikiwiki), for an internal information repository (used to be svnwiki), and for software development repositories (linux-libre, irpf-livre). access to the top level is limited, and different permissions over different subdirs are granted to different sets of users
Thanks, Alexandre. This trick of essentially using one unified repository as multiple repositories (starting at different subtree levels) is an interesting data point.