When installing SQL Server, you get to specify SQL Server administrators, i.e., the list of users initially in the sysadmin role. By default, this list contains the current user.
(Image quoted from https://msdn.microsoft.com/en-us/library/dd578652.aspx.)
This default value strikes me as odd. Wouldn't
BUILTIN\Administrators be a more sensible choice than the current user? After all, isn't the whole point of Windows authentication not having to manage two separate user/group directories? And local administrators can gain sysadmin rights anyway, if they want to, so it's not really a security feature either.
On the other hand, SQL Server was written by people much smarter than I am, so there might actually be a very good reason for this default value. What is it?