Dear Heather et al.,
I am glad that we have someone from Ushahidi subscribed to our list :)
Anyway, back to the issue of the Google competitions: yes, you are right that the challenge didn't result in an editor retention. However, I personally think that the challenge was a success. I define success here by the following:
-There is now an (upcoming) Kenyan chapter that has arisen as a result of the Google competition.
-The Kenyan chapter is, IMO, very active and rejuvenated. This has led us into carrying out quite a number of Wikimedia-related events like offline Wikipedia projects, Wikipedia takes Nairobi and talking at various events.
In short, the Kenyan chapter and all these aforementioned activities were as a direct consequence of the Google competition. So it may have not served as a good tool for editor retention, but it very much aided the Wikimedia movement in achieving its mission and Strategic Plan (specifically with regard to offline and increasing reach) in Kenya (the "Global South"). However, the editor retention problem has been one of my personal concerns, and that was the primary reason I started WikiSaturdays -- where chapter folks gather one Sat. every month to edit (although, arguably, they haven't been as successful, thus far).
So, with the upcoming Google challenge in Botswana, I would not solely analyse its success with the number of editors retained after the challenge, but how the challenge assisted Wikimedia to achieve its overall mission and/or strategic plan in Botswana.
Sincerely,