That's certainly some serious evidence in support of his addictive nature. How much time each day would you have to spend on HN to get 50K in karma, even allowing for a person who has a high level of quality submissions and comments? Seems like it would take up a significant chunk of one's life and I could see why he might want to quit cold turkey.
While this is true, there's a reason that the mean isn't always used in descriptive statistics: outliers can easily skew this. I've had a few multi-hundred-point submissions, for example, and while 64karma/day is nothing to sneeze at, you'd just need one or two really solid comments or a good submission per day.
Then again, considering the way I'm phrasing this, maybe it's more of a sign of my own addiction rather than something a reasonable person would say...
For me, the discussions in the threads are the best part of HN. The submissions are great; but what brings it all together is the discussion.