I'd venture to guess that the difference between a requirement of just 1 endorsement from users with karma >= 1 and the current HN is fairly significant (a downvote differs conceptually from a nonexistent endorsement), so you may not be able to approach it too closely. I suppose only time will tell though.
This is an excellent observation. It takes effort to downvote someone; it takes zero effort to ignore a pending post that doesn't meet whatever your standard is for endorsement.
Basically, it turns the system on its head; it's no longer "Bad posts will be removed," it's "Your posts will automatically be removed unless someone decides that they are good."
I'm actually really optimistic about this change; it will force people to be more civil if they actually want to participate. However, it will only work if lots of people are willing to put in the effort of endorsing quality posts.
This reminds me of the 'penny gap problem': that the steep drop-off in users from raising the price from zero to a penny is much larger than the (much smoother) drop from further price increases.
