I don't know if I'm really, really behind on this, but I had no knowledge of this story.
GamesRadar put together a feature on game glitches that became features. According to them, the original Super Mario Bros. wasn't supposed to have question mark blocks that popped out multiple coins. This was a glitch that the programmers set out to scrap. They actually changed their mind when they saw how that multi-coin glitch impacted gameplay. The idea to have one coin per block was scrapped and the glitch became a feature.
Link
Source:
http://ift.tt/1g1EjoA