I've always wondered how we always see leaked Zune HD, PS3 Slim etc.. pics and almost never see any Apple product pics leaked until the day it's announced. I know their employees sign NDA'S but they must threaten death to those who leak info.
Wirelessly posted (BB 8900: Mozilla/5.0 (iPhone; U; CPU iPhone OS 3_0_1 like Mac OS X; en-us) AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7A400 Safari/528.16)
In addition to very strict NDA's, rumor has it new/proto poducts are kept very secure, in passcoded areas with very limited access, etc.
Apple is a complete hardass and is completely overprotective of everything. I guess you have to be when your entire business model is based on the misconception that every other company in the world copies Apple's ideas.