In this case it is clearly intended to be deleted under users, so why not use the language feature for that (destructor) instead of inventing yet another level of book-keeping.
You can, as long as you don't need to know if/how something within the deinit failed. If you literally just want to know if the item is gone, that's exactly a weak_ptr.
File streams, say, do this by expecting users to close() the file themselves if they care if exceptions happen, but if you destruct without doing that first, any exceptions are caught and don't make it out of the destructor, so they're just gone and you'll never know.
