It is fiendishly difficult, and most sites that try emulating Slashdot or Metafilter fail. Clearly these sites have something their imitators lack, and whatever it is, you can't buy it at Ebay or Amazon. Possibly it is good, functional engineering that fosters conversation. Maybe it is simply credibility. I admire these two community sites and their creators.
Community is hard, content is hard, and readers are the only judges who matter.
ALA currently has 100,000 readers, and that scares me because it makes me responsible. If ALA ever becomes useless to me or to you I will kill it without a qualm. Meantime we have a mission, and we also have a weekly deadline. In apologizing for this week's lack of content, I have created this week's content. And without that stupid, inflexible deadline, these thoughts about content and community would never have been voiced.