The biggest benefit I see for identifying frequently-visited locations is that it provides a shortcut for the system to narrow your location down much more accu

The biggest benefit I see for identifying frequently-visited locations is that it provides a shortcut for the system to narrow your location down much more accurately without relying on the full GPS+WiFi location-based tracking. WiFi network + frequent location can probably put you at your house, your office, or your bus stop almost instantaneously (with corrections coming as GPS updates), meaning that using location-based services like Find my iPhone, map routing, or (my most frequent use case) nearest bus stops and their times, can be accomplished much faster and with less battery life. Likewise, a poor GPS location + frequent locations can narrow you down much faster even with WiFi turned off. As long as this data is stored only on my phone and not provided wholesale to applications, I'm fine with it; otherwise, it's concerning.