Example of a real-life graph with a "hole"? Anyone ever come across a real non-textbook example of a graph with a hole in it?  
In Precalc, you get into graphing rational expressions, some of which reduce to a non-rational.  The cancelled factors in the denominator still identify discontinuity, yet can't result in vertical asymptotes, but holes.
Thanks!

I guess the derivative of the absolute value (on the reals) comes up in certain "actual" applications. It is undefined at $0$, and no way of plugging the hole makes it continuous. Which doesn't prevent one from defining arbitrarily a value of for instance $0$ at $0$, but it seems better to just leave the hole.
