Zillow provides free neighborhood creative-commons boundaries btw: http://www.zillow.com/howto/api/neighborhood-boundaries.htm
Just using NYC, the Zillow data isn't perfect. But then, the larger point is that no-one even agrees what these different neighbourhoods are anyway, so it's very difficult to come up with a definitive data set.
Re:Mapping the World
by toomuchtodo on Wednesday January 07, 2015 @05:30PM
(#8853767)
Has this data made its way into OSM yet?
It looks like it's distributed under a CC-BY-SA licence. OSM actually changed from CC-BY-SA licence to ODbL because it didn't look like that CC licence is suitable for geo databases like OSM ( read more: http://www.osmfoundation.org/wiki/License/We_Are_Changing_Th... ).
It would have to be relicenced (which I presume would not be a problem since ODbL is spiritually very similar to CC-BY-SA). But as maxerikson mentions it's not clear that it should be in OSM
Re:Mapping the World
by maxerickson on Wednesday January 07, 2015 @05:45PM
(#8853855)
Zillow would have to grant additional permission, OpenStreetMap only accepts data under rather liberal terms (because then changing the distribution license does not have to be a debacle).
"Fuzzy" boundaries are also sort of controversial (i.e., there are more than 0 people who will always speak against them).
Here is Flickr equivalent http://code.flickr.net/2008/10/30/the-shape-of-alpha/ (downloadable). Foursquare also does similar work.
[edit: sorry, I thought Airbnb was analyzing listing data to find the extends of neighborhoods. They don't seem to do that.]