Buddylist Auto Add for roles

I am building a social networking site, and I wanted to exclude certain roles from having a buddy auto-added. I have attached a patch that I believe gives that functionality. It works with the Auto Assign Roles module so that when a new user registers and is auto assigned a role, buddylist auto add checks to see if the new user is in one of those roles.

My patch is mostly conceptual code, and has not really been tested, but I wanted to throw the idea out there and see what people thought.