Why doesn't C++ make destructors virtual by default for classes that have at least one other virtual function? In this case adding a virtual destructor costs me nothing, and not having one is (almost?) always a bug. Will C++0x address this?
You don't pay for what you don't need. If you never delete through base pointer, you may not want the overhead of the indirected destructor call.
Perhaps you were thinking that the mere existence of the vtable is the only overhead. But each individual function dispatch has to be considered, too, and if I want to make my destructor call dispatch directly, I should be allowed to do so.
It would be nice of your compiler to warn you if you do ever delete a base pointer and that class has virtual methods, I suppose.
Edit: Let me pull Simon's excellent comment in here: Check out this SO question on the code generated for destructors. As you can see, there's also code-bloat overhead to be considered.