I'm showing my personal bias, of course. I just launched a business/economic social news site called http://newsley.com.

But, far from being parasites, social news sites expose readers to a much greater cross section of news than a local newspaper ever could. And, a well moderated social news site like Hacker News or a heavily filtered reddit is much more useful than an editor could ever be. There's still a whole lot of room for news aggregation/content crap filtration online. Social News is just getting started.

But then, I'm probably preaching to the choir here on HN. :)