I know for sure if you make a second account and sign into a device like a phone or tablet where you've already signed onto another account - it will realize th

I know for sure if you make a second account and sign into a device like a phone or tablet where you've already signed onto another account - it will realize the connection and start suggesting you friends from your original account. I'm not sure if that's taking MAC address of the device or the phone number into consideration or what - but it's definitely a bit creepy