On Maemo News we solved this by enabling downvoting of submissions (well, aggregated feed items), and by making downvotes worth 5 upvotes. The unpleasant side-

On Maemo News we solved this by enabling downvoting of submissions (well, aggregated feed items), and by making downvotes worth 5 upvotes. The unpleasant side-effect has been a slight tendency to shoot the messenger by downvoting relevant-but-unpleasant news. But in general it has helped with story quality