While I also like "Not Just Bikes" and this idea in general, I must say that urbanists sometimes make this mistake - living right next to a dozen of people next door and a hundred more in the same building doesn't mean that you will talk to them. I've lived in the apartment for all my life and changed it last year. I have no idea who are the people next door to me, I don't know their names and the whole social interaction with them is limited to "have a nice day" once every few weeks when we accidentally meet in the corridor.
The other benefits of the higher density living does work though. More small businesses and shops nearby, hobby points of interest in the 15-30 minutes distance on foot or bus/tram, better infrastructure, etc.