Bad idea...

If you've read my post you'll notice that I agree on the panty stuff. But creating a "members only" forum will only make the stereotype worse instead of better:
" secret underground networks where "no one" knows what is "exchanged" "

...that kind of hysterical media crap.

If I really had to choose between secret forums and letting people openly posting these "panty moments"...I'd go with the last one.

YogiBear - "Captain's Log...today I've spotted panties on 3 girls. In the following 2 pages I have noted the time and place I have seen them followed by a full description of the panties; including color, size and optional patterns printed on them"