Originally Posted by
noglider
A lot of the map data is crowd-sourced. When you see a problem, report it. This is why it keeps improving. I have submitted corrections to Google Maps, and they have accepted them. I understand that pretty much all of Africa's maps are crowd-sourced. Amazing, eh?
Most of Google's map data is from Google. Most commercial companies provide ways for the public to provide corrections.
It appears that Openstreetmap (OSM) is the largest (by far) crowd-sourced map database and, at least in the US, it started with a huge amount of publicly-funded (governmental) data. I suspect that's true for Africa too. (And editing OSM data is assisted, in important ways, by commercial companies, such as Bing, and governments).
Regardless, there are many places where the OSM maps are the best available. From what I've experienced (mostly in the US and some in Germany), my opinion is that the OSM maps are very good. But, in areas well covered by commercial firms, the commercial maps are more complete and accurate. There are, more often than one might expect, fairly major things missing or wrong on the OSM maps (I know because I fix them!)
Still, I like the OSM maps (well enough to take the effort make them better). But they aren't perfect.
None of this is meant to discourage people from using OSM (in some cases, you might not have a choice) but to make sure people's expectations are realistic.