This story by David Kravets at Wired News shows just why companies need to be more serious about translucent databases. Even if the database is usually protected, mistakes can be made. Operating systems can fail. And even when that doesn't happen, programmers can forget to implement an important rule.
The problem in this case seems to be a programming error. They collected information about people under 13 years old even though they weren't supposed to do that. But why collect any of this personal information when you can allow people to share information in anonymous or translucent ways?