A whole set of interventions we've discussed revolve around the idea that encouraging users and showing them the impact of their edits will help them to be more active and successful. I personally like these ideas—I get excited when I get messages from Yelp, for example, telling me that hundreds of people saw my review.
But I just stumbled on some research around a very similar initiative. The experimenters set out to discover whether providing positive messages such as "25 edits. You're doing great!" lead the recipients to greater heights of editing activity.
The question gets asked and analyzed systematically in a variety of ways. The answer, across the board, seems to be that there is no measurable result. What do you think? Are you convinced by the findings? Or do you think the experiment was flawed?