According to this zdnet article, when plugging your iPod into an Ubuntu machine the device is mounted without ever being prompted for a PIN code. This is working on non jail broken iPhones. I’m surprised the article only names Ubuntu — surely this must work for other distributions? Unfortunately I don’t own an iPhone to test first hand.
On a side note, is Ubuntu taking over the world? Sometimes you don’t want to make things too easy otherwise all of the idiots will flock from Mac and Windows and plague all of our favorite distributions with requests for ports of ___ (insert favorite fan boi single platform software here).
iOS 3 and below did not protect the cryptographic keys. The keys should now be protected in iOS 4+. Also you can use a pass phrase as well as a pass code.
Read here: http://support.apple.com/kb/HT4175