Hm, making it optional (but default on) is a reasonable thought. Two points I wanted to make clear, to make sure we're really on the same page:

1. The proposal is just to warn, not to halt -- not sure if that satisfies your concern your comment about "throw{ing} an error in production that, while it doesn't effect the final outcome of the calculation, does leave the User with a feeling that not everything is right with the world."
2. As I just finished writing in another reply, these errors are of the non-fatal variety. Sometimes, it's important to know about it (to, say, inform program logic), but not something that needs a "fix", per se. Yes, die and friends could be used for this as well, but there are some acceptable reasons why the design team chose this path.

That said, I want to reiterate that supplying a 'verbose' option to control the "carp on DESTROY" function might not be a bad idea (thanks!), though a consuming module could always just override DESTROY if the warnings were inappropriate...