Its not so much that it feels like cheating, its more the impact of a module like Memoize might have on the underlying system that concerns me. It is entirely possible for an inexperienced developer to build a program that runs entirely fine on their test system, however on a production system is far too memory hungry and causes more problems than it solves.

Yes, I am aware that Memoize gives you options to limit the memory footprint, however that then trades off against the performance boost (and quite possibly entirely negates it)

So yes, in my job where I regularly deal with data sets that can easily fry servers with over 100GB of RAM, I can and do justify spending time finding the most efficient algorithm I possibly can and avoid using memory hungry workarounds such as Memoize. Then again, we spend a lot of time doing research for every aspect of our systems, as the more efficient and faster they are, the more productive (and therefore more valuable) they are.

At the end of the day though, everyones environment is different and likewise the development focus and priorities are different.