Google writes “it’s no surprise that geolocation services are becoming more popular with people than ever before, and that many companies are adding locations functions to respond to this demand and improve the services they offer their users. For e.g., Twitter allows users to geotag their tweets. Everyday, millions of twitter users on a PC or mobile phone choose to do this. Knowing that someone is posting from Bangkok as opposed to Manchester gives followers an important perspective when they read a tweet about ‘red shirts all over the city.’ On smartphones like iPhone, Palm, and Android devices, services such as Google Maps for mobile, Yelp, and Urbanspoon use location to provide relevant local search results, while apps like Foursquare and Google Latitude let you find your friends on a Friday night. But how does this work? How do smartphones actually know where you are? Lots of people talk about GPS (the satellite-based global positioning system) but a lesser known fact is that GPS can be slow: it can take tens of seconds and sometimes much longer to “fix” your location depending on the specific hardware and your physical location,”.
More info: The importance of geolocation services