The most long-lasting and engaging communities are those where people help each other to solve real challenges: — make money — save money — build a family — become healthier — become happier
The absence of this mechanic makes the community really weak because people don't have time to waste on talks with no outcomes.
Here are some examples:
Google Each time they entered a new country, they focused on educating digital marketing agencies on how to make money with Google AdWords.
I was an executive at a large agency in 2009, and we made $1m+ during the first year of selling Google Ads, which was a blast for our business.
Now they help app/game devs to make money by selling digital goodies.
Microsoft When they promote a new product, they offer huge premiums for vendors and resellers. For example, they gave $500k+ to each of our local system integrators to help ramp up MS SharePoint departments back in 2012.
Amazon Amazon helps merchants make money by selling stuff on their platform.
Apple They help app/game designers to make money via App Store.
Lululemon They make people healthier by attending yoga classes and special events.
Catholic Church Californian Missions, Medieval Crusades, and many other events were highly profitable (yet risky) for the participants.
Army Life in the army is challenging even if you're not battling real enemies. That's why there are so many veteran organizations in the US, and the Swiss/Israeli army is considered one of the best networking options for locals.