I've routinely voted up people I disagree with because I thought this was a place where opinions across the spectrum were to be encouraged. It would be sad to see this is now not the case and that instead you should say whatever's most likely to get you points. Are the people on the leaders board meant to be the most "average" in opinion as judged by HN readers? That sounds downright boring.
Of course, you might just be saying that's how people use downvoting, not how they should use it - which I'd agree with. Even so, a sanction against this practice would be super as it removes one's motivation to actually express one's true opinion (unless burning karma is one's hobby).