how was the current threshold derived? has there always been a newbie "wait period" or was it added after-the-fact and the parameters tweaked? it's something i've suggested to a few other forums i've come across that have spam issues.
Originally there was no restriction. For a very short time the limit was just 50 posts. Then the current time+posts restriction was put in place. These numbers work alright. If I wanted to stick with newbie restrictions forever, I'd probably add some more restrictions so people couldn't lurk for 4 hours and then post 5 posts in a few minutes.
It's planned to remove these newbie restrictions in the future, once the moderation system is improved. I don't like blocking drive-by contributors. It should require almost no effort for an unregistered user to post something. The low "barrier to contribution" is how 4chan and Wikipedia got so popular.