I can't wait until SME Server has an ldap backend. Please please please.
SME Server will only have an LDAP backend when someone (or some group of people) wants it enough to develop it, or to pay for someone else to develop it. The Easter Bunny is not going to drop it off fully formed.
If you go to the bug tracker you'll see that I've made a few mods to add LDAP auth backend, but there's still lots more to be done.