

How does Facebook know who I interact with offline? - talltofu

I got a friend recommendation from Facebook that has me worried about how intrusive it is. 
This is a person with whom I have NO mutual friends. I only know him because our kids attend swim lessons at the same time (along with 30 other kids). Here is the kicker though, I have not communicated with him using any digital source. We only talk when we meet and have just exchanged phone numbers once but never called each other. I don&#x27;t know his email&#x2F;twitter&#x2F;LinkedIn&#x2F;Facebook details and he does not know mine.<p>So here is my question - how does Facebook figure out that I have interacted with him? Sure, we both pay for the swim lessons with a credit card so they can parse through that and figure out that we pay for the same activity. But then why is he the only one on the recommended friend list? Why isn&#x27;t another parent (who I don&#x27;t interact with that much) also on there?<p>Any thoughts?
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valarauca1
Geo-tagging.

If you both updated your status, or used facebook messenger from the same
location multiple times. Facebook assumes you either met, or know each other.
Since you attend the same place at the same time.

Stuff like this is why I deleted facebook. If I wanted to know these people I
would add these people, I don't need suggests based on literally spying on my
day to day activities.

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talltofu
I replied earlier - but no, that's not a possible answer. There are close to
100 kids there at the same time. So about 100 parents checking Facebook at the
same time. Why only him? Also, both of us are in the pool with our kids
(parent-toddler sessions), so no Facebook for us

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basdw
As Tomtoise said, they indeed read your address book. Even if you do not use
the messenger app Whatsapp. You have given permission to let them read your
whole phone (sms, address book and even to make changes in your calendar
without your consent), by installing it. That is the main reason why many
people do not install the Facebook app, but only use it via a browser.

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talltofu
I actually just checked my address book and it seems I have never saved his
phone number as a contact! The only other explanation could be that he saved
my phone number as a contact and let Facebook have a field day with it

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tomtoise
Facebook app synchronizes with your address book. My best guess is that you've
left facebook sync on and forgotten about it, added his number. Facebook has
looked up that number, seen it belongs to this friend of yours and suggested a
facebook friendship through that.

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talltofu
Is there a setting for that? I don't remember permitting Facebook to access my
personal data. But then again, knowing their constantly changing privacy
settings, who knows what they are upto

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talltofu
I just checked that I had never saved his phone number as a contact - I just
gave him a missed call probably so that he could have my number

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czbond
Have you both checked in on Facebook at the swimming pool? You might have also
used Facebook multiple times at the pool, where they geolocate you, and then
find people that have similar geolocation at same time, same place?

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talltofu
Valid point. But then there are close to 100 kids there at the same time. So
about 100 parents checking Facebook at the same time. Why only him?

