The way it's done now is that all new submissions are nofollowed until they hit a certain karma threshold. A while back when I looked at this, the threhold was

The way it's done now is that all new submissions are nofollowed until they hit a certain karma threshold. A while back when I looked at this, the threhold was about 3-5 up votes. This is actually a very neat and simple way to exercise editorial control to remove the nofollow: if enough people in the community like it, there is something useful about it and it is vetted.