As far as I know, currently only YC backed companies can post on HN jobs.

To make it more broader (and perhaps more useful), anyone with more than a certain karma threshold (e.g. 500) can also be allowed to post a job opening on it. A certain number of karma points (e.g. 50) can be deducted for making every job post. This strategy would keep it clean and free from recruiters, and since the post is coming from a 'accredited' HN user, it would possibly have a good chance being interesting and useful enough for most of us.

The additional problem this would solve is that it would allow job postings to be visible for longer durations than what's possible with regular news threads.

Just a thought.