The newbies group is not required for SOM to work. It just adds another layer of protection. Most people set up the newbies group to not allow users to post links and then once they have been vetted, the have it move them into the trusted group (registered users) - that way, you don't have to moderate every single post manually. You can just assume that if someone has made 'X' legitimate posts, they are probably real and don't need to be moderated in the registered users group, which would save a lot of time on a very busy forum. On smaller forums, it might not be needed.