Could we possibly add a button to share on HN/Slashdot? I find that I rarely share articles on Facebook/Twitter because not all my friends are programmers and instead go straight and share the URL on Hacker News. Do you think we could add a button to directly share articles? The audience is much more focused on those sites and it would be easier for everyone.
Sharing on Facebook, Twitter, and LinkedIn is an intentional action to ostensibly share with people you personally know: that is, you're sharing with your social graph because you think the people who follow you would be interested in it.
Sharing on Hacker News, Slashdot, Reddit, Digg, and others is not the same thing: it's submitting a story to essentially a news service. The act of personally sharing to those services doesn't really have any value.
For example, let's say I share a question on Facebook. At most only a couple hundred people are going to get the link from me, and I'm reasonably confident that if those people are interested in me, they'd be interested in taking a look at a question about whatever I thought was interesting enough to share. The same with Twitter or LinkedIn: you don't get the question unless you're actually following me. If you then share the question to your social graph, it's quite likely there's not going to be a huge overlap: I don't know the same people you know.
But let's say you post the question on site like Hacker News. There is only one, shared user base of hundreds of thousands of people you don't know. You have no idea whether those people care, you don't know if those people are qualified to answer the question, and more than likely, nobody is going to have any idea it was you who shared it.
And that's the real problem with providing easy sharing for news services: nearly every question that doesn't get closed on Programmers.SE gets up-votes. Every question here is interesting to somebody, and with the massive amount of traffic services like Hacker News, Slashdot, and Reddit get, it's quite likely every question could get shared, multiple times, by different Programmers.SE users.
That sucks for everyone. It sucks for us because questions get exposure by a disinterested audience who cares more about attention-getting headlines than providing expert answers, and it sucks for news services because we're actively encouraging people to resubmit stories to the same, shared user base.