I really like this quote:

Bingo Card Creator is not terribly complicated software when compared to most applications, but it sits on top of other pieces of code (Rails, the web server the browser, the TCP/IP stack, the underlying OS, the hardware on both ends, etc) which _collectively_ are orders of magnitude more complicated than any physical artifact ever created by the human race.

You can insert any number of one-off business applications, reports, queries, etc in place of "Bingo Card Creator" but the concept remains true.