Note - this is not an Oracle question - but something as food for thought. Appropriate I think as graph is now a big component of the product...
While on vacation in Colorado last week, we decided to head up to Crested Butte to see a local play production. My wife, searching for a local motel on a site I will not name, found one with great ratings that was quite reasonable and about "30 miles" away. Not being from Colorado, she went ahead and booked it, and then told me where it was. I shook my head. That is no where near 30 miles away, at least by road - it is on the other side of the mountain!
Obviously this company uses a point to point with nearest neighbor "as the crow flies" method. While simple points might work reasonably well for small areas, say in a city road grid, it is a horrible solution for larger areas and places like Colorado. With mountains that take hours to drive around, those 30 miles or so turn out to be 90 miles of road and take about 3 hours to drive based on posted speeds!
Needless to say, I was upset. After spending almost an hour on the phone to get this all straightened out and the bill credited, I thought I'd point this out. Not only for "buyer beware" - but mainly as a good example of what not to do when designing map-based systems for consumers. KISS is usually a good approach, but in this case it is a horrible one when a road network with speeds AKA network data model graph solution is required.
Thinking further, even in a city grid you have one-way streets, parks, longer blocks, etc., which can make the real distance (by road) much further than "as the crow flies". So I'm not sure nn is really good for any such "close to me" analysis tool.
And yes thanks, had a great vacation. Miss the cool weather from my native state!