First time I've heard of this. Then again I went to a land grant university of 25000 undergrads. I'm assuming these are more common at smaller colleges.
Facebook started at Harvard, a 20k student school. It might be more of a tradition at the old East Coast institutions - growing up on the West Coast, I've never heard any reference to anything of the like.
Well back in the 70's I had an American teacher and in one 6th form general studies class (on American culture) she mentioned the concept.