Frankly, you need a lot of developers and servers before investing the time to setup a ldap deployment, integrating it with logins, and spending the inevitable hours debugging why nobody can access anything anymore, becomes more worth it than "just rsync/pssh into all servers and edit /etc/passwd".
Actually, if I had to do it, I'd use chef to automate creation (and destruction) of user accounts over an LDAP any day. Chef can be a pain to learn and use, but any sort of LDAP is even worse.
I think there's a lot of fear and hate surrounding LDAP, but that's mostly for historical reasons. LDAP has gotten a lot easier to set up. Even in 2009 a colleague and I set one up (using openldap) and had other machines authenticating off of it in an afternoon. It's gotten even easier than that since then.
And hell, you should be using Chef to set up your LDAP master and slave. So once you have the config correct once, you can bring up another machine without trouble when needed.
We're on LDAP, which we use to SSH into our ec2 servers, and which we use for authentication when we deploy using `git push production master` to a GlusterFS cluster. We're running our LDAP, application, and file servers on Gentoo. We can easily add new accounts, and we have it set up with group permissions (so the friend can deploy game content to test but not prod, for example).
I refuse to believe that LDAP is "too complicated" or "has to scale before it's useful", when a couple of guys can, in their free time, set it up for themselves. It's saved us a load of time in managing servers that would otherwise take away from the limited time we have to actually write code.
It's also a whole lot cleaner than a bunch of Chef scripts running a script across a quantity of servers; using Chef can too often be a crutch to fixing the actual issue.