Altruism doesn't exist, and this is not a bad thing. To 'provide help', even anonymously, is to help yourself by bettering the environment in which you live ("Karma" sans magic).

I don't think anyone has posted any sort of story or comment to HN (or read HN for that matter) without some hope for personal betterment as a result.

As far as chilling trends in the future, I see HN as 'the new Slashdot', and I'd be more afraid of it following similar patterns over the long term.