Sure a PIN can protect you from having the average thief dig into your data but someone with more technical knowledge and a computer running Ubuntu Lucid Lynx can easily navigate into the guts of your iPhone, even if it is locked and not jailbroken.
According to Engadget: “The belief is that they’re just a buffer overflow away from full write access as well, which would surely open the door to making calls. Bernd believes the iPhone’s lack of data encryption for content is a real problem, and also cites the inability to digitally sign e-mails as reasons why the iPhone is still not ready for prime time in the enterprise.”
What can you do right now to protect your data? Nothing. Just cross your fingers hoping that Apple will soon enforce data encryption for its devices.
You can read the full report here.