[nostromo]

I suppose it's a bit of a bigger problem than that since a lot of information on Facebook is shared with friends of friends.

Because of this it's not just a problem for the bad user (like my aunt on FB), but also all of their connections (like me and 300 other people).

[yaix]

True. But still, you can just set your privacy options to only share this stuff with first-level friends.

The real problem with Facebook is that they collect data about you, without you being able to control that data. Everything that people have in their smartphones about you, or that other people add about you on Facebook by other means (uploaded email address books, etc) is agregated into "your" profile, even if you don't actually have a profile on Facebook.