I beg to differ on this. The Zagg kept your glass from crack/shattering everywhere and kept it contained. I would say it definitely did it's job.
Last year my HD2 got knocked out of my hand, hit glass-first on the asphault. Yes, the glass cracked, but the screen protector kept it front falling out. My digitizer was not affected, so overall I can still use the phone. But had it not been for the protector on it (which was zagg, btw) the glass would have been all over the place and would not be able to use the phone at all due to possibly being cut by the broken glass.