The bar at Zoetrope
Powazek advocates raising the bar in an electronic community-- making it difficult to participate in order to deter irrelevance and casually malice. The Zoetrope writers community has a significant bar!
First, it's hard to find; this might be bad design but it's probably deliberate, recalling one version of Dreamless.org that had a secret URL.
Second, you have to register.
Third, after you register, you learn you're only a probationer; until you write five reviews of recently-submitted short stories, you have very limited access.
This encourages active participants, makes newcomers share the work, and chases away freeloaders. In a field rife with wannabees who want the perks but can't or won't do the work, it's a very clever idea.