People expect machines they interact with to behave in some kind of logical manner. After 2 or 3 times of submitting an article that HN has traditionally liked -- and watching it tank -- just not that motivated to submit more. After submitting my own articles, having people stop me in the hall and tell me they liked it and voted up for it on HN, only to see it have no votes? Not so motivated to submit more. After the tenth conversation about how people expect HN to act one way and instead it acts another? Not so crazy about it.
I think the problem here is that PG wants folks to participate, but only to a certain extent. People want to interact with the system, but on some kind of mutually-fair terms. I'm not sure PG's goals line up with the average user any more. There are good reasons for this, and I'm not trying to trash the entire effort. It's just that this is a tough problem. I don't think you can code your way out of dealing with messy human issues at scale. If you could, we'd all be managed by computers in 50 years, and that's not a future I would wish for my children.
Got a better idea? There's never been an easier time for one to start their own link aggregator site.