One of my pet hates is development/aid initiatives that do not consider what already exists. This is a problem for two reasons. Firstly, if you don't know what is going on around you, you don't know if you're duplicating. There is anecdotal evidence, for example, that school children in more well-resourced/stable areas of the Cape Flats are often involved in 5 or 6 different HIV prevention programmes (each with a different approach, funding stream and monitoring system) at the same time, while those in very poor/less stable areas have no such opportunities. Secondly, if you don't know what is going on around you, you can't link in with what other people are doing to increase the impact of your work.
Mapping may not be able to provide the information locally yet, but at a national and regional level, checking what else is happening for possible duplication and integration utterly crucial for "value-for-money" and Not That Hard.
This mapping exercise (via AidData) is a great example, using the DRC:
analysis and for planning, evaluation and thinking about what might make things better for people on the ground.
More maps of awesomeness for better, smarter aid!