This is a great conversation that I’ve had with a few people already.
Short answer: I know and appreciate Marj and I know the folks who organized some of the neighborhood email groups. There aren’t any secrets — and free-flow of neighborhood information is the main reason that each one exists in the first place.
Long answer: I think listservs and wikis do different things. The yahoogroup format seems to work well, especially for messages targeted to certain interest groups: neighbor activists, the business associations, etc. It's good for alerts, when information is time-sensitive. It's also good for just dialogue. Yahoogroups don't seem to work quite as well when the group grows or diversifies to the point when many of the messages are irrelevant, or when there's just too much volume. Spam can sometimes be a problem. It's also a clumsy way for several people to collaborate, because everyone gets everyone's input in installments, which can be tough to parse through.
Columbia Citizens provides an online place for any one project or discussion. In a wiki, we can create and update content as if it were in a studio or anyplace where people can design together. The Citizens' Wikli is a good example of a collaborative wiki-project. In a listserv, the ideas can be more like so many ping pong balls bouncing every which way between people — difficult to focus and to form. Unlike a listserv, Columbia Citizens makes it easier for neighbors to casually find content — sometimes months old but still relevant — and to take stock of a work in progress. They can just visit and don't have to sign up to look or to participate.
Columbia Citizens is generally less email-intensive (except when it’s ginning up Wikli interest), which means people have to find their way to each topic, and they need to keep checking in. Wikis aren't as familiar as email. For some people, Columbia Citizens could be more engaging than a listserv, but it can also be more anonymous. Wikis aren’t prone to abuse and tampering, because any changes are pretty easy to wipe away before they get wide readership. Edits in a wiki might be more contentious and frustrating: heck, everyone's a critic, and this could be a critic's free-for-all. So the pros and cons are different.
I think it's possible for the various lists and tools to work together. Any group can talk through its listserv and work together in Columbia Citizens when that format works better. Columbia Citizens has a directory of local email groups out there. If we want this wiki to behave a little more like a listserv, I think I can also figure out how to set up straightforward RSS feeds, which would let people select wiki pages that interest them and receive updates when people make edits.