I'm new and stupid, but why not just put an admin account in ldap and ditch the rootdn?
Many sites choose to do exactly this. It depends whether you consider an ACL override capability more useful (which it argubly is) or dangerous (which it argubly is).
One question I pose to the list in light of recent features: Let's say you use (2.4, ACL-aware) back-config and totally flub the ACL config. This should be correctable with the rootdn (which will trump the broken ACL config). If you choose to not configure a rootdn, do you find yourself in a mandatory restart situation that might otherwise be avoided?