My impression is that pg wants to encourage the hacker spirit by providing a bare bones service which could easily have a 'hacked' api built upon it.
Certainly, if I have had access to it I know I could do some pretty useful sociology on HN's audience (= the pool of startup hire material).
If you have a fabulous idea for how to use the data contained on this site, I'm sure everyone will be impressed and interested to see it.