Like others have been mentioning here, Metafilter has a fee like this, and from what I hear, it works really well for them. Thinking about it more, though, I c

Like others have been mentioning here, Metafilter has a fee like this, and from what I hear, it works really well for them. Thinking about it more, though, I can see how it would could really prevent new users from wanting to join. I'm not sure exactly what would happen. I'd be willing to support an experiment and try it, though.