A corollary to "lying to your players":
if you do fancy tricks behind the scenes, but the players can't tell the difference, you might be wasting time with those tricks.
this tends to come up a lot with random generation; a lot of times shuffling various things does not actually lead to different situations or create a meaningful feeling of uniqueness (and sometimes isn't noticed by the player at all) and thus... doesn't add as much as it could
any sufficiently complicated backend system is indistinguishable from a random number generator!
