Signed up with a fake name and throwaway email. Was asked to enter mobile number for verification.[1] Entered mobile number and verified.
The top few 'People You May Know' suggestions were all people who I know have that number on their iPhones, all of whom use the Facebook for iPhone application. (It obviously happens if they use any platform's app to sync contacts, not just iOS)
Don't have the time to check now, but I would imagine Facebook uses this exact same method for suggestions if you use your primary email to sign up. People who have you in their email contacts - and have imported them to Facebook - are probably suggested to you too. That way you'll know who keeps you in their email address book too.
[1] Note: to trigger the SMS verification stage, you have to enter a semi-obviously fake name.
"People who have you in their email contacts - and have imported them to Facebook - are probably suggested to you too."
I noticed this behavior when I signed up to test this first using an old email address. It had known friends as suggestions as well as people who had already requested to be my friend, including my actual profile. I don't explicitly remember important my email contacts but it is a possibility.
Looks like it treats both contact books the same, even if a user didn't add the individual contacts at the time of import, it keeps a record of them to potential make suggestions at some future point in time.
Signed up with a fake name and throwaway email. Was asked to enter mobile number for verification.[1] Entered mobile number and verified.
The top few 'People You May Know' suggestions were all people who I know have that number on their iPhones, all of whom use the Facebook for iPhone application. (It obviously happens if they use any platform's app to sync contacts, not just iOS)
Don't have the time to check now, but I would imagine Facebook uses this exact same method for suggestions if you use your primary email to sign up. People who have you in their email contacts - and have imported them to Facebook - are probably suggested to you too. That way you'll know who keeps you in their email address book too.
[1] Note: to trigger the SMS verification stage, you have to enter a semi-obviously fake name.