"It's an emerging rule of thumb that suggests that if you get a group of 100 people online then one will create content, 10 will "interact" with it (commenting or offering improvements) and the other 89 will just view it." LINK
Seems about right for Cavechat. The list of who's online usually shows about 10% of viewers are registered and the rest are guessts. And most registered users don't post. Interesting. I guess Cavechat is pretty normal.