I've been thinking a lot about why people share in communities, so this was a cool take on things. I'd tack on to the 3 P's that communities need members who are:
1. Motivated.
2. Empathetic.
Maybe these are no s* sherlocks. But I say motivated because people need incentives, whether it's the prospect of making money or building a reputation or getting recognition. There is something everyone is after, and many of even the best communities have some sort of reward system (HN & Quora off the top). And empathetic because members need to be able to relate to each other. If the sharer has high empathy then maybe less so. Here's a longer winded version of what I wrote: http://marketinghead.tumblr.com/post/31338994971/why-share
As I write this, maybe the closer community members are sympatico, the more likely you get community wo incentives needing to be so significant...
Hmmm. Interesting post. I might say that the closer community members are, the more the reward or incentive is getting to know the other members rather than fame or money. After all, that is the reward for interacting with offline communities based on close ties like family. Well, except for interactions with that rich uncle /sarcasm.
As I write this, maybe the closer community members are sympatico, the more likely you get community wo incentives needing to be so significant...