I think Nicholas Carr made an interesting distinction in The Shallows about the usefulness of tools in the context of short and long-term memory (interesting even if I feel ambivalent about it):

"In freeing us from the work of remembering, it’s said, the Web allows us to devote more time to creative thought. But the parallel is flawed. The pocket calculator relieved the pressure on our working memory, letting us deploy that critical short-term store for more abstract reasoning. As the experience of math students has shown, the calculator made it easier for the brain to transfer ideas from working memory to long-term memory and encode them in the conceptual schemas that are so important to building knowledge. The Web has a very different effect. It places more pressure on our working memory, not only diverting resources from our higher reasoning faculties but obstructing the consolidation of long-term memories and the development of schemas. The calculator, a powerful but highly specialized tool, turned out to be an aid to memory. The Web is a technology of forgetfulness."