

Ask HN: How does Google and Facebook do friend recommendations? - inthewind

Today I was dismayed to see a notification on my partner&#x27;s Android device, which read along the lines of: &#x27;Do you know Joe Bloggs&#x27;.  Joe Bloggs being me.  I&#x27;m not sure just how Google has joined the dots.<p>My partner has a Nook HD with a Google play store account.  Mainly to download Google apps for Android, they also use the on board Chrome browser.  I have a Gmail account, but I have never sent mail to their Gmail account or the other way around (they don&#x27;t use that account for regular mail).  My partners primary email account resides with another email provider, and is accessed through the on board Nook email client.<p>They have also installed the Google Keyboard and Facebook apps.  Though I don&#x27;t use Facebook.  Neither of us have Android, Microsoft or iPhone smartphones.
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bmarker
Can we instead have a discussion about recommendation "engines"? I've been
interested in writing one for fun but I have no clue where to start in
learning about them. Can someone point me in the right direction, maybe a
Coursera/OCW course?

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chewxy
There is an old OReilly book (2006) which deals with this. I think it was
called Programming Collective Intelligence

~~~
inthewind
[http://shop.oreilly.com/product/9780596529321.do](http://shop.oreilly.com/product/9780596529321.do)

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inthewind
I mistakingly signed up to Facebook with a work email in the past. And noticed
many work acquaintances appearing in Facebook's: do you know lists. Which I
can only attribute to other people sharing their email address contacts with
Facebook, and Facebook holding onto that data.

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inthewind
This shows that Facebook have already have you as an entity in other people's
networks before you have even joined Facebook. I guess you can cement yourself
within those networks by adding them as friends, or saying that you know them.

I guess they also watch to see who you look up, and from that see if there are
any connections between those that you look up, those friends might appear as
further recommendations.

It can be quite spooky sometimes. The interesting thing with that account is
that I never friended anybody, so it's interesting to see who comes up in
their list. Some appear quite random, but others I recognize.

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CWIZO
I'm always surprised when I see people say stuff like this. For me every
recommendation on every social network was more in the line of 'SELECT user
FROM users ORDER BY RAND()'.

I guess I'm doing something right.

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rankam
I would think, similar to Netflix or Spotify, that they would use machine
learning algorithms (ensemble technique) to perform collaborative filtering.

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msoad
Where did you see the recommendation message? Facebook or Google Plus?

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inthewind
Sorry I'm not that offay with Android. I think it was a system notification, a
'Google' one. I doubt it was a Facebook one. And my partner doesn't use
Google+ actively as far as I know. They may have stalked me, I'm not privy to
their surfing habits.

They don't really use their Google account for anything but Google play, but
it could be tied into their Chrome browser/profile somehow.

A long shot could be that we both visited the same *.wordpress.com site today.

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anxiousest
Usually via graph, a "six degrees of separation" sort of thing, you don't have
to directly contact each other, but it's enough to contact some of the same
people to assume a connection. Also similar use patterns or geo locations (ip
location or profile input indicating physical proximity) can be taken into
account. I don't have intimate knowledge of their algorithms so I don't know
about any other factors they might use.

I find it quite amusing that you're "dismayed" at a system working properly :)

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inthewind
I think it would be a breach of privacy using geolocation data.

The reason I'm dismayed in this instance is that I can't work out how the
connections are being drawn.

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anxiousest
I'm just guessing.

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inthewind
Aught wrong with a guess, but that one could get quite creepy pretty quickly.
Say you were at a small conference in a small building in the one room. And
Google started to suggest those around you as friends - that could be quite
useful - but equally it could blow someones cover.

Also you spot a large car with tinted windows nearby, and suddenly Google is
suggesting that you might know a certain someone that maybe in that vehicle.

You might loose your privacy if you were living in a block of flats and this
were the case.

Certainly an interesting idea as to whether they do use your geo-data.

Now I'm pretty sure that profile data such as where do you live, or publicly
printed location data could be used. I.e. with Facebook, it's probably more
likely to hook you up with people that are geographically close - but I'm
speculating here too.

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anxiousest
I was thinking about less granular grouping i.e city or state level.

~~~
inthewind
A good question in itself, would be where do you draw a line. At what radius
would you feel comfortable?

I'm posting from foo to a bar forum. Will bar tolerate someone from foo?

