In my opinion Geekhack fine how it is. Or at least make vendor forums visible to people with under _______ amount of posts (if this whole visibility thing goes into effect).
I've never had a problem with people with 0 post when I'm selling something (often times, people just want to buy something, it kinda screws vendors by not making vendor forums visible). When buying, I'm a bit more cautious, but if I get screwed, I have no one to blame by myself and them. Not GH or 60 post or 3 months of membership....