It seems clear that location services are doing better outside the United States. The user's location is displayed on an area map on the PDA screen. That's a remarkably involved system, and NTT DoCoMo's ability to sell it might seem encouraging. However, Japan is a special case. Japanese cities are notoriously difficult to navigate.
Street names are increasingly popular but still are far from universal.
It's as if you gave a friend directions to your home by first giving him your ZIP code and then telling him what landmarks to look for. Travel guides warn tourists to expect taxi drivers to stop several times en route to a destination for further directions. In that kind of environment, it's not hard to see why customers might snap up a service like DokoNavi. On the other hand, it lessens the service's value as a predictor of success in other markets. There's also the European example to consider.