Hi David, 
really thanks for this email.
I'm at OAI8 (conference of Open Access in Geneva), with several fellow wikimedians, 
and I'd like to express some thoughts related to yours.

On Fri, Jun 21, 2013 at 6:47 AM, David Cuenca <dacuetu@gmail.com> wrote:
All this led me to think about the emotional vs rational rewards that users (or institutions) obtain from contributing content to Wikipedia, Commons, Wikisource, etc. Are really "active thanks", as currently implemented, suistainable and scalable? Will all the contributors who deserve it get a thanks some day? Could personalized view counts/ratings reports about uploaded pictures, major contributions to WP articles, etc. have some impact on contributor satisfaction/retention? Would "automated personal impact reports" free collaborators from the duty of thanking one another, or would that mean less personal interactions?
These are some questions that I leave open here. 

I think this is a crucial point.
It is not new that people do things for all kinds of motivations, that is for all kind of "rewards". 
We know that "being appreciated" is a fundamental boost in human nature, and we have seen this in Wikimedia projects as well.
I want to connect this thing with a related issue, which is participation of scholars (phds, professors, students, researchers, etc.).

It is my (strong) opinion that when we will find a way to track/report detailed authorship and contributions of users in collaborative environments, we would have scholars come to us and really collaborate. 
As most of you know, the academy world is trapped in "publish-or-perish": people need to publish articles with their name on it, because articles (and citations of article) is the real currency in the academic world.
Scholars need to "produce", and on that production they are evaluated, and their career depends on that.

What if scholars could report to their universities how much they contributed in Wikipedia? How many useful comments they have written on academic blogs? How much thought the gave in specific and high level threads in mailing lists? (yes, I know it's a dream)
If we could create the report/feedback framework for people to collaborate and be "commoners", we could make academic collaboration skyrocket (IMHO). 
We could start thinking about this in the Wikimedia world.  

==Semantic annotations ==
As you might know there is a GSoC [3] which aims to convert the OKFN Annotator [4] into a Mediawiki extension. That is a great project that will enable inline comments in mediawiki projects, but it shouldn't be seen as the end, but only an step in the direction of semantic annotations.
What could semantic annotations mean for Wikipedia? More precise answers to questions. Instead of just having "millions of articles" there would be the possibility of answering "trillions of questions" (or at least pointing to the text fragment(s) that has/have the answer). This kind of paradigm shift might need some pondering and broad community discussion.
What could semantic annotations mean for Wikisource? Text interconectedness. Be able to relate concepts, authors, fragments... and then be able to query those relationships.

Another dream of mine is an annotator that could save "facts" in Wikidata statements. 
We could reald a newspaper online, or a book, or an article on a scientific blog, and highlight a short sentence, and this sentence would be a statement (Item has a Property Value), with a source (the original document).
I bet this is not *so* difficult.