Mostly speculation, but I do have a fair amount of experience in marketing, economics, and growing websites... That can happen if you reach a maximum audience.

Mostly speculation, but I do have a fair amount of experience in marketing, economics, and growing websites... That can happen if you reach a maximum audience. In other words, everyone has seen your website decided to stay (or not) and unless they have a new reason to come back they are gone forever. I suspect Hacker News may have hit critical mass because they have as many new members as leaving members. They received a fair amount of attention a few years ago and now are kinda "old news" for many people. Unless they improve retention rate or have a mass influx of attention (i.e. featured on CNN, Reddit, etc.) perhaps invent something new, it will remain relatively constant (or decline if they screw something up).