Even though the article is mainly about ATF issues, I assume it can apply elsewhere - and that this can apply to all mobile devices, laptops and desktops, not just iPhones:

Headlilne: Apple deluged by police demands to decrypt iPhone]

"That is something that I don't think most people realize," ... "Even if you turn on disk encryption with a password, these firms [e.g. Apple] can and will provide the government with a way to get your data."

[Without Apple's help,] ... estimates [are] that if a user chooses a six-digit passcode, the maximum time required to guess the number would be 22 hours, while a nine-digit PIN would require two and a half years. A 10-digit PIN would take 25 years. Average times, of course, cut those maximum brute-force durations in half, and that could be whittled down much further if it's possible to guess PINs a suspect is more likely to use

Truecrypt is open source and does not have backdoors that "corporate" products have just in case they need to access your information.