Also, OSM allowed the amazing initiative of http://hotosm.org/ to be built -- a website where contributors from around the world help humanitarian organizations by adding data into OSM for various areas where people are in grave need (e.g. finding houses of people in drought areas in Africa) based on satellite & aerial imagery. I tried this, and really couldn't walk away much too far into the night, can get addicting... also I think it's something similar to analyzing photos from spy satellites during WWII, only for 100% good case! For more details, see:

http://wiki.openstreetmap.org/wiki/Humanitarian_OSM_Team

Quoting from the wiki page:

"From the beginning of OpenStreetMap it was anticipated that open, free map data would be a tremendous benefit for humanitarian aid and economic development. The idea was proved during the Haiti earthquake in 2010. HOT was incorporated in the immediate aftermath, August 2010, as a U.S. nonprofit and became a registered 501(c)3 charitable organization in 2013. Anyone is welcome to contribute to the HOT mission via our Tasking Manager - all you need is an OpenStreetMap Username. We ask only that you try to uphold the same code of conduct as our members, see our HOT Membership Code."

Surprisingly for me, quite many important buildings can be discovered without local knowledge (i.e. without "being there physically"), purely based on aerial imagery and a specially crafted guide. See e.g. the following link, with some hints and clues on how to recognize a school for a current (urgent!) pre-typhoon task http://tasks.hotosm.org/project/804:

http://wiki.openstreetmap.org/wiki/Humanitarian_OSM_Team/Typ...