In C++ it's quite easy to get burned by keeping a reference to something where the owner went out of scope eg.

   class Foo {
      int bar;
      int& getBar() { return bar; } 
   }

if you take ref of bar and Foo goes out of scope well fuck. It gets even worse, eg. :

    vector<int> foo;
    int& bar = foo[i];
    foo.push_back(1) 

that last line can cause foo to reallocate the buffer and bar is then invalid, meanwhile that code will compile without warnings (well I'm guessing it will I haven't done C++ in a year :) )