If you are worried about hardware backdoors, just imagine if your PC or laptop had a real hardware backdoor that would allow an attacker to connect remotely over LAN, Wifi or 3G to access your harddrive, your RAM, your display, your keyboard, your microphone, your camera. It would render any and all of your attempts to protect your privacy null and void, including any encryption. Something immune to software protection or detection, completely OS independent, in fact, even independent of the main cpu and therefore impossible to detect. Something that works out of band, even when your PC is powered off. Something that you cant disable, even if you think you can, because it can remotely be enabled again. All it would take is someone having the key to this backdoor
Sounds far fetched? Yet if you have an intel laptop or PC with AMT/vpro; thats precisely what you got.
http://en.wikipedia.org/wiki/Intel_Active_Management_Technology
And it would be a stretch to believe some 3 letter agencies wouldnt have the keys.