HN is still supposed to have a fairly narrow range of topics. With the userbase growing so quickly, a lot of people may not read the guidelines and the content could start spilling into subjects not really meant for HN. In that case, I think just educating people about what should and probably shouldn't be here isn't bad.
Or maybe offer folks who spam the site with partisan politics, profiles of "dating tricks" classes, and ad pitches a script that will redirect them randomly to Reddit or Facebook.
People should be able to do whatever they are able to do. If it's supposed to have a fairly narrow range of topics, use the voting system to achieve that.