I weighed in with this over at AVC today…
“community” and “network” are not quite interchangeable, but the strongest networks are also communities.
If your service doesn’t provide more value to a user than she contributes, it will not become a network. I give a dollar and get 3 back, I’m going to come back the next day.
Add your music library to Napster, get access to thousands of others.
Comment on AVC, and get value from interaction with other commenters, from comments themselves, and relationships.
Join Facebook and connect with friends, get access to their endless stream of manufactured memes 🙂 (oh and they joy of sharing their life experiences, photos, randomVille).
And if your service doesn’t allow me to share content and opinions with other users, it will not become a community. The strongest networks are also communities.