This same question has come up over the last week as I've been working with a group of colleagues on a definition of community journalism. I'm not sure we're any closer now with a group of community journalism scholars than that group of doctoral students was 25 years ago. But the discussion is still worthwhile.
A Nieman Report published this summer from Michael Skoler does a great job of looking over this issue, considering the importance of viewing communities as something more than just an audience with shared characteristics. He writes:
"[N]ews organizations need to think of themselves first as gathering, supporting and empowering people to be active in a community with shared values, and not primarily as creators of news that people will consume."
You can read the whole article here.