I think the purpose of group-types is often misunderstood, e.g. when you have a simple intranet site and want to give certain privileges to a few users such as employees and customers, I've often seen people create a group-type 'employees' and then create a single group of this type 'Employees', while it would have been totally sufficient to create it as the default group-type 'group'.
Creating new group-types only makes sense when you want to define extra attributes with the groups of this type.
This misunderstanding is caused by the confuing UI I guess.
