Good overview article in Nature by Ben Laurie and Cory Doctorow, motivating and introducing Sovereign Keys and Certificate Transparency.
Worth reading to get a good understanding of the problem we have and some innovative solutions under development. The "old" PKI model failed to scale securely and new infrastructure is needed. I expect this is a dynamic we'll see repeated. The rapid growth of the internet and the application layer on top of it will continue to challenge the mechanisms we deploy to secure it.
Thanks to boingboing for the link - http://boingboing.net/2012/11/17/what-do-we-do-about-untrustwor.html