Not everyone has willingly given their social graph to Facebook. Facebook builds shadow profiles on non-users and then fills them out with, amongst other thing

Not everyone has willingly given their social graph to Facebook. Facebook builds shadow profiles on non-users and then fills them out with, amongst other things, data it gets from their actual users that they didn't no they were sharing. This is particularly sneaky when Facebook has used dark patterns to trick app users into granting them permissions they don't strictly need for service.