Ivan Krstić, former director of security architecture at the One Laptop Per Child foundation, has joined Apple, to, as he puts it "work on core security for a California fruit vendor." Speculation will abound that this hiring demonstrates a need for better security modelling within Apple; in reality, it seems that Apple have recognized an incredibly talented asset, and will no doubt benefit greatly from this move, as future Apple users will also benefit.
During his tenure at OLPC, Krstić designed the Bitfrost security layer for the XO laptop, an application model that runs applications in separate application contexts in order to prevent malware and intrusion (in some ways a similar approach to Google's Chrome browser). Again, in Krstić's words, Bitfrost was designed to be "both hard to break and easy to use. If this proves successful, a future version will make ice cream fall from the sky."
For more information, however, I would highly recommend following Krstić's personal weblog, which I have found to be both entertaining and informative over the past few years. I am hoping that one big gain from this move by Apple will be adding an element of transparency to their organization, if Krstić continues writing as he has in the past. I am looking forward to following his further adventures.