Plus geolocation almost always fails on a phone in my experience, the IPs generally come from the datacenter of the carrier (my old Alltel phone always said I was in Alabama, almost 1000 miles away).
If they used HTML5 geolocation instead, they'd burden the user with an annoying authorization popup (at least on the browsers I use).
edit: (The lesson, then, is to not do web geolocation unless it strongly enriches the usefulness of the site (map-related sites, etc) or your hand is forced. People rightly don't want their location freely-shared and people are rightly annoyed by location-sharing-confirmation popups.)
