auto classes and finalizers

[Jarrett Billingsley]

"Sean Kelly" <sean at f4.ca> wrote in message 
news:e10pk7$2khb$1 at digitaldaemon.com...
>     - a type can have a destructor and/or a finalizer
>     - the destructor is called upon a) explicit delete or b) at end of 
> scope for auto objects
>     - the finalizer is called if allocated on the gc heap and the
>       destructor has not been called

Would you mind explaining why exactly there needs to be a difference between 
destructors and finalizers?  I've been following all the arguments about 
this heap vs. auto classes and dtors vs. finalizers, and I still can't 
figure out why destructors _can't be the finalizers_.  Do finalizers do 
something fundamentally different from destructors?