I'm trying to understand what Atlassian crowd does over an LDAP server? It looks like most Atlassian products allow you to point to an Atlassian server for authorization/authentication. If that's the case why use Crowd?
LDAP provides you just Authentication/Authorization. Sometimes more. Atlassian Crowd offers Single Sign On. When you have multiple web apps, e.g. Confluence, Jira, Fisheye, etc you don't want to sign on to each one of them, if you're singed in on one.
Also Crowd offers OpenId, which means that you can use it with any app that supports OpenId. LDAP requires configuration of each application to the corresponding LDAP Server.