Intentionally introduced errors are a helpful strategy when work must be reviewed. 1) I’ve insinuated a small error into my reports to ascertain whether it was actually being read. E.g. “If you see this, call me.” 2) When preparing an apartment for a housing inspector I leave an easily-fixed code violation for the inspector to find instead of something difficult to fix. 3) To thwart copyright violations, map makers secretly introduce fictitious towns. Proving piracy consists of finding the fictitious town.
Perhaps something like this belongs here.