If you look at the top users most of them submit thousands of stories.
For example mklopez[1] submitted 16k stories were only 10% hit the frontpage and LtGenPanda[2] submitted 2,481 with a 42% popular ratio.
You can see this stats at the bottom right of the user profile on Digg.
I think nickb is still the top submitter to HN, there are about 4250 submissions from him, runner up is cwan with 3750 and then edw519 with 3180, I wonder what the top 3 on digg looks like.
For example mklopez[1] submitted 16k stories were only 10% hit the frontpage and LtGenPanda[2] submitted 2,481 with a 42% popular ratio. You can see this stats at the bottom right of the user profile on Digg.
[1]: http://digg.com/users/mklopez
[2]: http://digg.com/users/LtGenPanda