I would guess that they're using Active Directory because they have Windows PCs to manage. AD, arguably, provides a _lot_ of value if you have any quantity of W

I would guess that they're using Active Directory because they have Windows PCs to manage. AD, arguably, provides a _lot_ of value if you have any quantity of Windows-based PCs that you want to manage centrally. I haven't seen any compelling third-party hosted offering to replace the SSO and Group Policy functionality in Windows client OS's that AD enables. Maybe when Samba4 reaches maturity that will change.