OpenStreetMap is my favorite community project in the world. Truly open map data is a huge deal, given how many companies are making money from the stuff. Long ago when I started OpenPhotoVR I'd dreamt of eventually integrating it with OSM, too bad it never gained enough momentum.
I don't see how. The maps used by OpenStreetMap are under a free license, Wikimapia is just proprietary (Google) maps with a bit of user data on top. It's like comparing Wikipedia to Encyclopedia Brittanica with user comments.