How Does Facebook Know I Know These People?

I just learned something interesting about Facebook.

I got an invitation to join from a friend of mine I knew from Boston. He now lives on the west coast.

At the bottom of the email it had a section of ‘Other people you may know on Facebook.’

And it listed two people I know from my church, one person who is another dog walker I see at the park, a friend of the family who is recently graduated from college, a woman who was on the volleyball team with me at my college a million years ago, and one of my dog walking clients.

So I started poking around online because it’s astounding how FB figured out that I know these people.

All the people have two things in common:

• They have all sent me an email at the same address my friend sent the invite to AND
• They all have web-based emails (hotmail, gmail, aol, etc.)

So here’s what I deduced:

1. When my friend sent me the invite, he made my email address known to Facebook.
2. Since those people have web-based email accounts, their address books are also web-based.
3. Somehow Facebook was able to access their address books and match my email address on it.

Interesting…and a little scary.

Here’s a related thread:
Facebook Friend Suggestion: How Does it Know???

This entry was posted on Monday, December 7th, 2009 at 8:58 pm and is filed under Misc. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.