Java and C# support the notion of classes that can't be used as base classes with the final and sealed keywords. In C++ however there is no good way to prevent a class from being derived from which leaves the class's author with a dilemma, should every class have a virtual destructor or not?
Edit: Since C++11 this is no longer true, you can specify that a class is final.
On the one hand giving an object a virtual destructor means it will have a vtable and therefore consume 4 (or 8 on 64 bit machines) additional bytes per-object for the vptr.
On the other hand if someone later derives from this class and deletes a derived class via a pointer to the base class the program will be ill-defined (due to the absence of a virtual destructor), and frankly optimizing for a pointer per object is ridiculous.
On the gripping hand having a virtual destructor (arguably) advertises that this type is meant to be used polymorphically.
Some people think you need an explicit reason to not use a virtual destructor (as is the subtext of this question) and others say that you should use them only when you have reason to believe that your class is to be derived from, what do you think?
The question is really, do you want to enforce rules about how your classes should be used? Why? If a class doesn't have a virtual destructor, anyone using the class knows that it is not intended to be derived from, and what limitations apply if you try it anyway. Isn't that good enough?
Or do you need the compiler to throw a hard error if anyone dares to do something you hadn't anticipated?
Give the class a virtual destructor if you intend for people to derive from it. Otherwise don't, and assume that anyone using your code is intelligent enough to use your code correctly.