One could get the lat/lon coordinates from the address of each data point and grid the city in any way you want.
One method to define neighborhood extents could be cultural instead of geographic by crowd-sourcing the delineation. If one can ignore the desire to draw a strict boundary at a major street, you'll find certain 'neighborhoods' spilling out of their original blocks. Perhaps adjacent areas with distinct histories start to define themselves by the same architectural historical context. Or a once strong border between ethnic communities might disappear. Gentrification might creep across a river closing the gap.
That would be better than trying to categorize things solely based on the historical convenience of the US Postal Service.
Myself, I might approach the problem the other way - trying to infer the existence of a neighborhood-like structure in terms of similar homes which are close to each other (apply clustering algorithms), and then measuring to what extent these structures overlap. This technique would hopefully place the 4th-and-King-at-Caltrain high-rise apartments and condos apart from the 19th-and-Arkansas single-family and converted-single-family homes.
Another idea could be to just price individual homes based on last sale, then map that, than use an algorithm to guess neighborhoods on price per square foot?
I forgot that appraisers' sites had the lat long. That is a great idea.
The second method is interesting and seems completely new.
How is it possible to get people to give you what neighborhood they are in? I bet we would find that good neighborhoods go much farther in to bad neighborhoods than they do in real life because of people who live their pronouncing that they live in a good neighborhood.
One method to define neighborhood extents could be cultural instead of geographic by crowd-sourcing the delineation. If one can ignore the desire to draw a strict boundary at a major street, you'll find certain 'neighborhoods' spilling out of their original blocks. Perhaps adjacent areas with distinct histories start to define themselves by the same architectural historical context. Or a once strong border between ethnic communities might disappear. Gentrification might creep across a river closing the gap.
These could all be fuzzy-mapped by residents.