DIY iPhone Screen Repair - Don't Lose Your Screws!
Screen damage to the iPhone 4 is likely to rival its predecessors in frequency, which means lots of people will hear that "pop" when their iPhone screen breaks. If you don't believe me, a quick Google search will show a number of iPhone experiments resulting in quick breakage. Drops from three feet onto a concrete surface can result in a shattered screen.
http://www.macnewsworld.com/rsstory/70565.html
