I, for one, have to say that I have no problem with casual observers. I think it's entirely possible for someone to be interested in a topic and want to learn something, but not really have anything that they care to say about it. I've browsed plenty of discussion boards without posting and I've posted maybe twice on the Survivor discussion board that I visit occasionally.

We say we want to be open to everyone. Well, people are watching, and as far as I'm concerned, they're welcome.

That, of course, doesn't mean they wouldn't be more welcome if they actually did post.