Cryptome recently published a page on their site explaining how the NSA could technically gain access to your encrypted machine if it has Bitlocker drive encryption enabled. If you are using a PC with a fresh install of Windows RT 8.1 then drive encryption is switched on.
Cryptome highlight that the Windows FAQs on drive encryption says that a recovery key for your encrypted device is uploaded to your SkyDrive (now named OneDrive) account to make sure that you have a means of logging into your device should you forget your password. This would be a reasonable expectation as the encryption was passively turn on, however it goes on to remind us that Microsoft’s SkyDrive/OneDrive was a target/collaborator of the NSA’s PRISM program which means tha NSA have keys to decrypt your computer.
The write up also mentions that device encryption is “supported by Bitlocker for all SKUs and that support connected standby. This would include Windows Phones” it follows with “Bitlocker provices support for device encryption on x86 and x64-based computers with TPM that supports connected stand-by. Previously this form of encryption was only available on Windows RT devices.” So it may mean that newer Windows 8.1 PCs come with this ‘feature’ enabled.
If you have data that you want to secure on your machine it’s better to check out whether TCnext the resurrected TrueCrypt suits your needs (they use the last good build of TrueCrypt and plan to release new version in future I believe). Obviously there are more reasons than paranoia to encrypt your disks, for instance you could have your device stolen, luckily your data would be encrypted. As for Windows Phone there really is no way around this predicament.
Linux allows you to encrypt your computer during the installation and does not backup keys to any online sources by default so this is likely a better option if you have data that you want keeping safe too.