IMHO solving the Facebook walled garden would be one of the most interesting startups to create today.

I've spent several months studying how to create tools that get around walled gardens (unfortunately they aren't mine and I can't open source them) but this is definitely a problem I wouldn't mind working on next. There are ways to get your information out of Facebook that would be extremely hard for them to counter, but it's a fulltime job to create something robust enough and maintaining it in the face of changes Facebook makes.