[secabeen]

If you're just using the Foursquare API, they don't. The search API call doesn't require anything more than Lat and Long: https://developer.foursquare.com/docs/api/venues/search

However, they also have their Pilgrim SDK, which you incorporate into your app to have constant, passive location data available:

> Welcome to the Pilgrim SDK—the always on, passive location detection engine by Foursquare. The Pilgrim SDK provides contextual awareness to mobile applications and connected devices to understand where and how your users are moving through the real world.

> By default, Pilgrim SDK runs in the background and pushes you visits when it detects a stop.

My guess is that the Pilgrim SDK includes the device Advertising ID in the data it sends back to Foursquare to implement this.

[bigdubs]

> The search API call doesn't require anything more than Lat and Long: https://developer.foursquare.com/docs/api/venues/search

That Lat+Long, the implied time of the venue search call, and some type of disambiguation user id is all you'd need to start building a location history for someone.