For those who are familiar with tptacek from HN but don't know why he's so respected in the infosec space: http://krebsonsecurity.com/2012/06/how-to-break-into-securit..., http://krebsonsecurity.com/2012/06/how-companies-can-beef-up...
The infosec (specifically, appsec) space seems very very interesting.