Why not put all this information directly into OpenStreetMap and render new image tiles?
When you include the factor of social interaction on this large a scale, the number of PoI's & polygons will increase dramatically. OpenStreetMap would be overwhelmed with PoI's and areas, managing and sorting it out and in the end they would realize: 90% is not even closely related to streetmaps. OSM contributors aren't getting anything in return for hours of their personal live spent on considerable work, except an always increasing level of quality of the open streetmap. Let every group, being it OSM as a basemap data-provider, or for example Mundraub as an Overlay-Data provider, collect and organize only the data relevant to the group's particular interest to ensure they continue to have fun with it.
Simply combine all these different groups of social/scientific/economical/agricultural/[…] interests into one presentation layer, where we can pick any shared information collection (DSpace-Overlays), we're interested in and also provide new input to these information collections as well. In Realtime. And when something is missing, simply create a new Overlay.