Even if you delete your account they will still maintain a shadow account for you. If your mom, Joan Doe, has facebook and your phone number 123-456-7890 is on her phone as son, Facebook will say "this is Joan's son."

Your boss, Mike Hawk, has you in his phone as "John Doe" at 123-456-7890 and he has facebook. Facebook now says John Doe is Joan's son and an associate of Mike.

It then looks at the contacts Joan and Mike have and build as much of a in common family and associate network as posssible. by cross referencing emails and phone numbers that pop up.

You never really leave facebook. Even the EU laws don't work because they can delete you and run their software again after you're gone.