Didn't Jim say at some point that he purposely didn't mention a particular neighbourhood because he didn't want people to visit, knocking on people's doors and such?
I don't know, but it makes a lot of sense; myself, i favour numbers on real streets that put a character's house in the middle of a large park for that purpose.
It does happen, I believe there are many people who have bothered residents in the street where Sherlock Holmes was supposed to live even though the number doesn't exist.
Not as such.
When Arthur Conan Doyle was writing, the street numbers in Baker Street only went up into the seventies; there was a London street reorganisation afterwards due to which 221B Baker Street is technically a real address, but a large bank actually occupies it and several other numbers on that street; there was a point at which they had a secretary specially to deal with letters to Holmes.