What is the optimal amount of fraud?

Nb: all questions for more context, clarity or for an 'it depends' option will be ignored

Fair play to the 66% of people who correctly answered that fraud is better than no fraud!

This thread from heartless libertarian Megan McArdle is as good an illustration of why we should not aim for zero fraud as any (gets into the 2020 US election as it was topical at the time but the pen story is the kicker here) https://twitter.com/asymmetricinfo/status/1326573144245755905

And here's a good thread I've shared before about public service provision in particular, where systems are very often over-zealous at pursuing fraud (real or perceived) to the detriment of what they're supposed to be achieving https://twitter.com/DmitryOpines/status/1244217276460654592?s=19