What's wrong with having a reference member in C++?

Question

While reading "C++ Coding Standards: 101 Rules, Guidelines, and Best Practices" I came across the following:

Note that using a reference or auto_ptr member is almost always wrong.

However, the text doesn't elaborate on why this should be wrong. So what is so wrong about having a class with reference members?

Answer 1

I think the text is telling you to avoid embedding in a class anything whose existence is out of the control of that class. References and auto pointers may refer to already deleted objects.