Hmm, that's an interesting point, I'm not sure how you could get around it, as I can see why it would attract new people.
Forward Motion has crit sections visible to members only, and within them, crit circle folders which are only visible to specific small groups of people.
Absolute Write requires a password to enter the crit section - I'm not sure if it is members only, though. Perhaps having a password ensures spiders/bots can't cache or pick up the pages - you could stick a password (as AW does) in the forum description so that newcomers and members alike could see it.
I'll shut up now
