installworld blows away /etc/services
/etc/services could contain user-modified entries which get blown away with an installworld. Additionally some dports modify /etc/services as part of their install process (e.g. mail/spamd). I think the easiest solution is to stop installworld from touching /etc/services, but that leads to a problem for how to deal with updating /etc/ files when you upgrade (a task mergemaster can do, but really sucks without having file idents).