Apple has changed the type of assembly screws used on iPhone 4's, macbooks, etc to prevent users from being able to remove them...easily. That is the keyword here. This is what I can't stand about Apple, did you sell me the device or not? Because its one thing to say "if you crack this mofo open, you don't have a warranty anymore" but its quite another to physically prevent you from doing it. I'm sure that other manufactures do this too, but this is yet another example of Apple saying "F U" to power-users/tinkerers basically any user that (can) help(s) with development of their products.
Here's a link to where to buy the screwdriver needed in case you're ok with voiding your warranty and want to tinker with YOUR device-> http://www.amazon.com/Pentalobe-Screwdriver-iPhone-generation-Silverhill/dp/B004IU9EDM (oops)
Source -> http://www.popsci.com/diy/article/2011-01/new-fasteners-iphone-4-apple-finds-new-way-screw-your-phone