Historically, BIND has had security issues which prompt installations as a non-root user. The BIND 9 series is a rewrite which much better security than its predecessors, but its reputation remains. That said, it's never a bad idea to run major services like DNS in a sandbox or jail to limit impact of an exploited service. It's still possible for someone to break out of one, it's just a bit harder. Running as a non-root user but not creating a jail/sandbox is a quick fix that might only require some file permission changes (named -n).
Right now the Roller Network is running BIND as a non root user, but not within a jail or sandbox. The dameon process that listens for updates also runs as the same user, and since it's Perl it has taint checking enabled. Since BIND has a reputation as being insecure, my feeling is that people will still try to exploit it, regardless of version. So it's probably a good idea to avoid running it as root.