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Comment by abalone | Hacker News Reader

> Foursquare knows where they are in real time, because it powers many widely used apps, from Twitter, to Uber, to TripAdvisor, to AccuWeather.

Holy crap, does Foursquare get your Uber location data and associate it with other services like Twitter?

This is starting to sound like a mini-Facebook. Call me cynical but I bet the only reason Crowley is even talking about this now is because they're trying to get ahead of the reckoning that's coming to Facebook for these kinds of data practices. He's positioning 4square as all innocent "hey we dunno if this is cool or creepy, let's ask people.." But is he really? Or is it an effort to appear like they are being transparent? If they really cared they would make it clear what they know about you. But you can bet they won't because nobody wants Foursquare tracking your Uber destinations and associating it with your Twitter profile or anything else.

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No. Uber gets location data FROM Foursquare.

EDIT: That is, the API call doesn't include info about the individual. Foursquare wouldn't know who the individual is for whom the request was made. Except, perhaps, in rare circumstances where they tried correlating them, themselves. Even then, Uber mostly uses it not to understand where a user is but rather the types of locations at a given address.

> No. Uber gets location data FROM Foursquare.

This doesn't make sense and contradicts the article. Don't apps have to send coordinates to Foursquare to get location names? Foursquare then holds onto that data and tracks you. Perhaps also matching it to other services with a unified ID.

Update to your edit: The article strongly implies that Foursquare has figured out how to associate location data from multiple services into a single view. Apps that use Foursquare are feeding Foursquare very detailed location data about you, even if they're only using it to look up location names. It means Foursquare is getting all your Uber destinations and all your geotagged social media posts. The article literally describes how they've taken this data and turned you into a "card" that tracks your ID across services:

He taps on one profile, called “Harry,” and a pie chart pops up that details the habits of the real person associated with that advertising ID. “Harry spends a lot of time in Midtown, sometimes goes to parks, and rides the subway,” Crowley says, looking over the data Foursquare has assembled from the person’s use of popular apps and geotagging services.

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.

> 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.

Various apps use Foursquare's API to query what is at a specific coordinate. Foursquare knows what queries were made by a unique device. That's it. Not sure why this is so controversial.

Right? All they’d know about you is your home address, where you take Ubers to/from, where you like to eat, shop, places you post from, your habits over time, and anything else they could correlate across the myriad apps that send your precise, unique location to them. NBD.

This is why "home" is a few blocks away from home in my Uber profile and why I allow it location services only when the app is running.

Everybody should do this as standard, and it should be in all the 'howto guides'!

how would they know anything about my unique device if an app is just using their API? unless the API requires 'unique device id'? Or are they embedding a foursquare sdk, which grabs that info on API calls?

A reasonably dense geo, timestamp and IP address event stream over time (ie. Multiple apps sending over time reasonably frequently) should have sufficient information to associate ids. However most ad tech companies including I believe Google and FB are very leery of doing this "Harry" type of stunt and arrange data pipelines in a way that this cannot be done at any aggregation less than a few hundred IDs and export anything beyond segment data to prevent re-identification. I'm very surprised these people are touting it

> However most ad tech companies including I believe Google and FB are very leery of doing this "Harry" type of stunt and arrange data pipelines in a way that this cannot be done at any aggregation less than a few hundred IDs

I would be interested to see any sources about this (I’m not questioning what is said in the comment, just genuinely curious about this topic)

> in rare circumstances where they tried correlating them

That is definitely not a rare circumstance. I would be shocked if any data company at reasonable scale was not actively doing that.

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