After some footwork on SL, I get the impression other mapping efforts have been tried, though some mainland residents have their reservations. Previous efforts appear to have attempted the lazy route of sending automated bots to do the mapping, which tends to unnerve people. That's understandable: Robots don't understand property lines, miss a lot of detail, tend to run into things and people, don't respect the defacto rules of the road, etc. Not to mention, people get a little bit creeped out when a robot does actually stop and start asking questions about where it wound up (if Number 5 rolled up on you in first life, and you weren't intoxicated or walking in Portland's Little Bohemia, would /you/ tell it what street it was on?).