Oh come on, seriously? I'm not saying it's the best thing ever, but it works well enough for the majority of small businesses. There is nobody who is really inconvenienced by having to use AD (it's not like most people would even notice). At least it provides a default and standard authentication system, unlike the hacks I've seen where people use rsync to distribute /etc/passwd and /etc/shadow to all machines (and don't get me started on that piece of junk OpenLDAP, I have yet to meet the first person who could build a complete and working centralized auth environment with it.)