A lot of people flipped out about this and they pulled the data within a few hours, but it was too late.
Now I see this article, which not only reports on the story, but also digs into what they can learn about particular users. It is appalling to me that they have published this. (I've lost a lot of respect for Declan McCullagh. Maybe he's trying to make a point about how damaging this sort of data can be?) But this article is only a small part of it; others have made searchable databases, etc.
There are multiple levels of tragedy here: I feel sorry for whoever at AOL published this, because they're likely to lose their job; I feel sorry for AOL, because even if this was just an overzealous employee the whole company is (justifiably) blamed; I feel especially sorry for the people whose secrets have been exposed.
And I also am more generally sad about how privacy is dying. From little stuff like customer loyalty cards, to more major stuff like government wiretaps, it's just that we don't care. Like: we all know the government can (and surely does) read our email, but we don't do anything about it. You only really realize it mattered once it's gone.