There's a lot of talk going around suggesting that community has somehow changed, fundamentally, because of the Internet.
I think that's wrong, but one reason may be that I've always thought of community as a social networking process.
That process once was limited to a slow, local network: face-to-face communications. Over time, as new communications and transportation technologies made it possible to communicate across time and space, it became possible to speak of "the community of astronomers." That usage describes a set of people who don't live together, but share a set of interests, largely know one another, and interact in some meaningful way, however infrequently.
The Internet has replaced the old slow networks (like "talking" and "mail") with one that's global and fast. Tools like Facebook and Twitter make it possible for us to maintain personal connections on a global scale. Community is still the same process; it's just been extended across distances that once presented barriers.
But while the Internet in some sense collapses space, place still matters in real life. There are exceptions, but most people have connections that are directly the result of physical proximity: The people you know through your child's participation in a sport, for example. The people who live on your block. Your church.
Internet zealots who proclaim the death of local life often are just projecting their own personal oddities onto the universe. Don't buy it. I'm actually one of those people with many more global connections than local. And my kids have friends who have moved away to St. Louis, or Salt Lake, or Korea, but stay in touch through social networking tools. But these networks exist alongside of connections that are maintained because of geographical proximity.
Those of us who care about local civic life should recognize that the same tools that make it possible for special-interest communities to come together without regard to geography also can work on behalf of special-interest communities that are related to geography.