For what it's worth, I got my current job with ThisOrThat from an HN job posting. Although this is waning a little bit, I still believe that a company that posts on HN is more likely to be clued-in than average, and that makes it worth my time to investigate. It goes both ways.
Better than not. It seeds the info to a lot of competent people.<p>But IMO, it would work better if people would stop making such ambiguous postings. I'm not going to tell my friend about this awesome opening I saw on HN if you don't actually say much about it.