Location, Location, Location.

The World Wide Web has never had it, because there was no ordinary way for advertisers to know where someone was sitting as they surfed. That has made it impossible for the local hardware store to advertise to its neighborhood, or for national advertisers to target their ads geographically. It has also meant that cities did not have the means to warn residents surfing the web of a broken water main, an approaching storm, a forest fire, or a flash flood.  That may be about to change.