I've banged my head against this User Generated Content ranking problem several times, and I keep getting back to there being some kind of trade: the user does

I've banged my head against this User Generated Content ranking problem several times, and I keep getting back to there being some kind of trade: the user does something, then the site allows them to vote. That "something" can be clicking through to the article, categorizing or tagging the article, or even betting or spending karma for the privilege to vote. But site developers know that if they make the user do "something", then they will lose users. To which I ask: is it worth having a user who is going to knee-jerk vote? I don't think so, but heck if I know anything about growing a huge site like HN.