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 like to keep mine on its own server, only because in my view its one of the most important servers in an organization, and keeping it on its own server helps admins do backups and other maintenance activities. And because the server is so important you don't want to have other developers mucking around on it in any way that could compromise it by accident.
Also if you have a bunch of developers and an active continuous-integration server running you could actually spike the cpu quite a bit and the last thing you want to do is have anything standing in the way of you committing your code changes