Should it be on the development servers or a Subversion server?
I suppose this could be expanded to any client-server version control system.
I keep mine on the development server, which also runs Trac, Apache hosting an automatically-updated copy of the project JavaDocs, and the CI build platform. A project would have to be of fairly epic proportions to require a dedicated Subversion server.
However, keep in mind that it is very important to keep your Subversion repository backed up on another machine in another location - your repository is your most valuable asset!