It is my view that the back glass of the iPhone 4 presents iPhone 4 owners with two practical problems. The first one is the risk of the back glass falling and thereby cracking and the second is the glassgate problem where the back glass of iPhone 4 gets scratched by particulate dust and over time ends up cracking.
In fact, the risk of the back glass cracking is quite high especially after the back glass has been scratched and your iPhone 4 drops. From a “strength of materials” point of view, the scratches that are caused by the glassgate effect form points of weakness within the back glass.
