I know you don't have it listed, but, for me it is generating "Organic Views" (Search Engine). It is nice to know that the knowledge I have accumulated on SEO is working well for me. It is a constant learning process that reflects my work. It's not only an achievement for myself, but for all those hubs that have taught me.
The problem with Social Networking from what I have noticed, is that they read it once and put it to rest. It is very rare that they should share it. They talk about it, they "like" it, but sharing is few and far between. Once the initial surge is over so are your views.
I am relatively new to HubPages and am unaware that you can view "Ups". Nevertheless, it is rare that I dislike or don't rate a hub up. The world is interesting and there are many great writers. It is hard not to appreciate their work. Perhaps this was in referrance to the "awesome, beautiful, useful, funny, interesting" which I feel rating beautiful on "How to change your oil" doesn't help you. I have had some weird ratings on my hubs, all though I do appreciate it.
I do however enjoy the accolades. It gives you something to work for such as leaving insightful and engaging comments, or how awesome it would be to make hub of the day. It feels like your options are endless, but, I hope we all write for the joy of writing and not for some reward.
That being said, the greatest reward is reading a comment. It is nice to know that your work has inspired them, taught them or perhaps made them laugh. Even if it is a single comment, it can make your day. I love engaging comments, even ones that disagree with the topic. It offers another point of view that I may not have already seen. Constructive critisism betters you as a writer and "Seller" (Many hubs are based upon selling an "idea" so to speak).
But, in the end HubPages did a good job at making sure that you know your work is being recognized. They are all very rewarding and allows for more growth and opportunity.