[Eric18]

You make many strong points in your critique of the overuse and misuse of electronic dictionaries. We often fail to consider what a new technology, even an educational one, replaces or displaces in our appreciation for speed and novelty. Electronic dictionaries can never, as you make clear, replace a live teacher or tutor in providing the immediate contextual clues.
Still, I'm not a big fan of banning practices or limiting student access to a tool which they find practical, valuable, and immediate. A better solution, it seems to me, remains creating a dynamic enough classroom and vivid enough definitions that students don't run to an electronic dictionary. A focused study of prefixes and suffixes, as you suggested, goes a very long way toward addressing students need and desire to both expand and upgrade their working English vocabulary.
Again, thank you for the informative and reflective post. You really nailed some common problems with electronic dictionaries - even if we disagree about the appropriate response.