[dublinben]

>stability and cost

If this were truly the case, they wouldn't be using Windows. It's mostly inertia in large organizations and for the general public.

[NeutronBoy]

I'm not a sys admin by any means, so I may be out of the loop here - but is there a viable alternative for management of tens of thousands of systems and users, outside of Active Directory?

As good as *nix/Apple stuff is, is it really feasible to run it at scale across an org, without building custom deployment tools each time?

[nitrogen]

There were giant UNIX networks before there were giant Windows networks, using things with names like NIS/YP and NFS. IMO building custom deployment tools is kind of the point of using not-Windows, but I'd wager Canonical, RedHat, and/or Oracle have something for central management and deployment of Linux systems.