http://life.khanacademy.org/tagged/kamensWhen writing code, sloppy hurts.
Using an extra unneeded step in a subroutine can make the whole process slow even if slight the problem will be multiplied by the iterations.
Missing symbols , unreal logic etc. can make bugs that are intermittent or fatal, but is perfection a good goal?
Your customer isn't able to wait forever, a complex of subroutines can interact in enormously complex ways debugging has a real potential for going on forever.
So at some point you gotta declare good enough and ship the product.
At Kahn Academy they are making a big teaching machine, the customer is millions of subscribers. Every error is experienced by each.
But you gotta ship the product , they can't wait for perfection, striving for good enough is constant and troubleshooting never ends.