I am not community professional, and I can't answer about mechanics, how it works, but I have some observations, that shows me — a great product, probably, impossible without a great community.
I was participating in three communities, which I name 'great', so let's start with the first one.
1. My profoundly loved home network community
When I was 24 years old, we (me and my friends) had changed the landscape of telecommunications in our town by introducing broadband internet access in times, when every young man was sitting on a dial-up modem. We have built the community of geeks, that was loving us, forgiving for any mistakes and service outages, because we were loving them. It was the time of BBQs full of tech speeches between close friends, belonging to both sides — the business and the customers. We were growing really fast before massive investments in the industry.
So, why the community was great? Nobody ever split customers and business, we were just geeks on both sides.
2. Impressive Terrasoft community
After we sold communications business, I was working in the company, that acquired us, to implement CRM solution, so I switched to the CRM topic.
I became interested in implementing CRM solutions and registered to vendor conference for partners. If you aware, it is visible, that the company is working hard to drive you in and forward. But only, if you are really aware (paranoid, like me, always is). After all, they are customer relationship professionals, so I couldn't imagine, that their community should be just geeks loving each other. I was participating 3 years.
Why is that community great? For me personally, because I have met people of the world of sales, really different from myself, we have discussed problems on their side, I learned from them about the things, I would never learn, being just the technical guy. And we were hanging out very well!
I haven't realized, that this difference in personality traits, that is the key to successful sales, just prevents me from doing well the job they do. Their community was so much organized to work toward the goal, that despite all problems with the new product, they expanded the sales, and later became the global vendor, recognized by Gartner and Forrester. That's why it is great!
3. Amazingly cool Umbraco community
The best community in the world today, as I know.
Never before, I saw so huge friendly group of people. The community consists, mostly, of the geeks on both sides of the business, loving the product and hanging out (I'm guessing what is more loved).
In a morning we run or do yoga (to sleep is the new option). During a day, we don't sell anything to each other, except the brilliant ideas. At evening, we travel on the boats, play the really huge bingo game, laugh, dance, drink, arrange games in the garden.
I am guessing how geeks, loving each other (again in my life), influence the company success, but it is.
Under the impression of Codegarden conference, that is just over, it couldn't recommend anyone anything, except to join the next time, especially, if you are a web developer.