For a long time at ScribbleWiki we had no revision control system in place, directly uploading all the edits to the server, and having a many different folders and a lot of copies of files. And having one could of stopped many problems. We deal a lot with MediaWiki’s extensions build by the community and even though we test them on a development server, things just seem to come up when we release it to our production servers and it would be awesome if we could of just pressed the revert button and have everything work.
Of course we like hosted products, why? We don’t deal with revision software we want people running it that know what they are doing and have it all working. We had a few options like the most popular pick lately seems to be CVSDude and then some others are Unfuddle and Wush. Although Beanstalk is what we went with, it has some great features like FTP/SFTP deployment so that with one button (or on each commit) it will deploy all of your commits.
Just a note that you should try and use SVN as it seems that is the new standard. CVS use to be but the developers from CVS created SVN and moved a lot of people over.
For some more information on code management and SVN: