So, mid-way through typing my reply I remembered this:
That should get most of your question, but I am also assuming you'd want more than one data point. So, I'll leave my reply below still.
I was wondering if any of you could tell me what some of the contributions users can make and how they are incentivized to interact with/contribute to the community?
Thanks for the clarification. I don't know if you've ventured through the primer, but that's usually a great start to understand the fundamentals. The primer mentions how users follow users as well as tags. That's the basis I'd answer your question with. Whether as an outlet or otherwise, Hubski is used as a medium to share news, information, art, technology, life-updates, troubles and more - similar to other social aggregators. The structure and size of Hubski is what makes for a more intimate experience. That is, through following users as well as tags, usernames aren't just that. On the assumption you follow tags because of your interests, the same logic holds for following users; you have shared interests with users you follow and users following you. Building some sort of online relationship(s) on one-to-one levels a relatively small community makes for a comfortable place to share material... alongside the community being encouraging of original content and thoughtful input. I get the feeling it's a bit more civilized and/or composed than your everyday big internet forum.
Incentives? Keeping up with the people you follow, finding and discussing news or ideas of interest. Also, regular posts like #pubski (happening tomorrow, so stick around for it), or francopoli's Today in History, or bfv's weekly music thread, or zebra2's reading thread. They are communal 'events' put on by the community for meaningful discourse. I guess my point is the goal is the same: a place to commune on the Internet for a thoughtful web.