Since the start several years ago, Nokia Maps, called Ovi Maps these days had offline navigation capabilities, i.e. maps data can be stored on the mobile so there's no data cost for navigation except for the few kilobytes of data required to get the A-GPS ephemeris almanac when the program is started to give the GPS chip a hint where the satellites can be found. This is not only beneficial to keep the delay down when scrolling through a map but is a bare essential requirement for me due to the high roaming charges for data as I often use navigation abroad. I guess I am not the only person with the problem which is why I find it even more surprising that Google still doesn't have an offline mode for Google maps. But perhaps its not so surprising because Google is a company that has its services in the cloud. So an offline mapping application doesn't make much sense for their product portfolio. So maybe that's the explanation!?