Should it be on the development servers or a Subversion server?
I suppose this could be expanded to any client-server version control system.
In addition to what other people mentioned about dev servers being trashed regularly, there is a performance argument too. If someone is doing some development or testing on the development server, you don't want that to slow down the SVN server for checkouts or synchronizations. Also if you decide to run something like continuous integration on the same server, you don't want all your unit tests to bog down regular dev/test operations on that server.