Regardez cette vidéo, si par exemple, vous voulez comprendre pourquoi des réseaux sociaux comme twitter ou facebook vous demandent votre numéro de téléphone...

<spoiler>
C'est pour connecter les habitudes de consommation de profils 'AFK', qu'ils achètent et dont ils ont le numéro, à ces comptes de réseau sociaux, ceci afin de mieux vendre la publicité sur ces derniers. J'ai calé la vidéo au moment où il commence à parler de cela.
</spoiler>

Extrait notable du transcript (plus rapide que la vidéo pour comprendre)
"""
And it turns out this information is actually being bought by Twitter
and it's being bought by large data warehousing companies,
from companies you've never heard of. Companies like CBG or Axiom
or Data Logics. They collect this information, not from the Twitter sphere at all,
they collect it from the real world. They buy this information from real world shops,
from credit card companies, from frequent buyer clubs.
They collect it into the database and then they sell this information to companies like Twitter.
Then Twitter takes that information from the real world
and it's connected with your Twitter account. So how did they do this connection?
How do they know who you are? Well, it's based on your phone number.
Because when you register for Twitter you will be giving in your mobile phone number,
and that's the key to the databases which are collected from the real world.
That's the reason why they're asking for your phone number.
That's the reason how they can connect your real world persona
with your online persona, so they know that this guy who's mostly tweeting
about football and is mostly following super models on Twitter
is actually this guy who's eating Rice Krispies and buys quite a lot of vodka
and is expecting a kid in the next six months. That's how they know.
"""