On behalf of authors everywhere, please don't use the flag button as a downvote button. This, for several reasons:
1. It's overpowered. Based on some experiments I conducted a year or so ago, it seems like 1-2 flags equal about 10-20 places dropped in the rankings. It's brutal. A single person in a bad mood can drop a story like a stone. I don't know the exact maths, but a single flag seems to have the effect of many downvotes.
2. It's not what it was designed for! According to the guidelines, flagging is meant to be for "spam or offtopic", not for stuff you don't like or disagree with and want to downvote. If you disagree with it, write a comment to explain why, or find a comment that agrees with your disagreement and upvote that. Flagging is not a way to express disagreement!
3. It's mean. I regularly get articles on the front page, and I don't care that much what happens to them (though of course I like to see the discussion they generate!), but once upon a time I did, and I'm sure that's still the case for many. When you put your heart and soul into an article, and it miraculously got picked up by HN, and it's on the front page, and people are finally checking out your blog, and it's getting more visitors in one hour than it had in the last 6 months... and you see the story suddenly vanish to the second page because someone flagged it... wow, that feels like a punch to the stomach. So please don't flag "real" articles, only flag spam/trash.
If you think an article sucks, post a comment to explain why you think so. Maybe you misunderstood. In any case, the feedback will be clearer. Please don't use the flagging sledgehammer to express disagreement.
(note: I don't know if pg would agree with the above, but these are my feelings)