This means if you can convince just 5 of your friends to quickly upvote your submissions, they will all get promoted to the top of the front page. You can do the same for their submissions. That's a six-person voting ring.
Ideally pg would like to detect these rings and assign your friends' votes a lower weight on your submissions.
It only takes a handful of people to get a story into a front page position where the votes can rocket upwards This means that the more people checking out /new and voting fairly (on average), the larger these voting rings would need to be to have any effect. (A war of numbers, sure, but "bad" stories would get flagged a lot more quickly too.)
A second problem is that the seemingly low engagement for /new can mean that reasonable items submitted at "bad" times don't make it past 2 or 3 votes whereas similar content submitted at busy times does well. In a good, fair system, that shouldn't be happening, but it's a reason I time my submissions to HN to strike when, I'm assuming, /new is at its busiest (4pm-10pm Pacific seems to work best for me). Without growing the international audience of HN, though, this might be tough to crack!
Hmm. I probably go to /new 10 times more than I go to the front page. I suspect the problem with /new is that there is so much of it (especially at those peak PST times) that stories don't have time to garner enough eyeballs before they are pushed off the page.
PS. Wish I could un-downvote - I just clicked the wrong arrow due to clumsiness, sorry... Upvoted another one of your agreeable comments to compensate :-)
Try: http://en.wikipedia.org/wiki/Trust_metric http://en.wikipedia.org/wiki/PageRank and http://www.advogato.org/trust-metric.html for a bit of an overview.