For me, my essay was the difference in attending the likes of Harvard - my essay was egregiously bad, and it was explained to me by the director of admissions of one Ivy League school via a family friend who was a professor at that same university as the primary reason for rejecting me, even though by all other metrics I was an almost stellar candidate, even out of those they typically admitted.
I wonder how many people have gamed the system like such, and what effect has it had on the lives of those who would have otherwise attended those schools? For me, I have miraculously succeeded in my path, although it was a pretty unique one - the confidence I built before college in my abilities helped me overcome the setback. There are many people not so fortunate though.
We probably will never know the true effects of such unintended gaming, but it goes to show that people shouldn't take as much stock in the school someone attended but their pure mind in industry.