I understand people are clumsy and the reason for using a case, but I don't understand why anyone would use a "glass protector" of any kind on the front. None of them are even close to the hardness, scratch resistance, and protection offered by the iPhone front glass itself. Not even close. In most cases it's plain old window glass, or soft plastic. The plastic ones can even *increase* the likelihood of scratching the glass underneath and ALL of them decrease the sensitivity of the touch screen to some degree.
Any impact strong enough to break the "protector" will also surely shatter the iPhone glass as well, especially now that the iPhone front glass is curved and the edge (which is the part that is most prone to impacts) has to be naked anyway. What's the logic behind, "I'm going to put this big ole piece of cheap window glass on the front of my phone." ???
When you re-sell this thing, you will have to slather it with solvents to get all that mess off, and the person buying it is going to think it's "pristine" when in fact it will be full of gasoline or whatever was used to get off the glue that makes it stick. That's not very nice.