Just to say I was pleased to come across another research paper that references ODK. There are three case studies - reporting pot holes, mapping ramps/barriers (eg for people with mobility difficulties) and points of tourism interest.
"Driven by the recent trends in the GIS domain including Volunteered Geographic Information, geo-crowdsourcing and citizen science, and fostered by the constant technological advances, collection and dissemination of geospatial information by ordinary people has become commonplace. However, applications involving user-generated geospatial content show dramatically diversified patterns in terms of incentive, type and level of participation, purpose of the activity, data/metadata provided and data quality."
Here's the link:
(I was not involved in this research so I can't provide the full paper)