[vintermann]

If 23andMe makes "shadow profiles", it would necessarily be for common ancestors, probably long dead. They can't see "down" into the genetic tree at all - whether great-grandma had 1 child or 13 they'll never know until the descendants take tests. But also, if 23andMe does this, they are short-changing their genealogy customers. One of the main things a genealogy customer would like to know about a match is if they're on the maternal side, paternal, or both (more common than you'd think, and mostly not because your parents are related). 23andMe, from what I read, does not do this - and that suggests that they're not getting much out of those shadow profiles.