Obsidian Entertainment - Realism vs What Designers Care About

Nathaniel Chapman uses his Obsidian blog for a rare entry, writing about Realism vs. What Designers Care About, Verisimilitude, and the Responsibility of Expectations.  I'll have to bookmark this one for those forum arguments because this does come up quite a bit; here's the intro:

Something that seems to frequently come up when discussing the design of a game system is whether or not some aspect of that system adheres to reality. Or, more precisely, whether the outcomes of that system accurately simulate the results that the person making the argument expects, based on their particular interpretation of reality.

Generally, these arguments come from players, or from non-designers, or less experienced designers, and will take the form of, "But XXXX isn't realistic!" or "Realistically, YYYY should happen instead". And, frequently, experienced game designers will turn around and say "Who cares?" and merrily go on their way designing an "unrealistic" system.

I wanted to give a quick explanation of why this is, explain what role I see realism as having in game design, and then provide a bit of a defense of "realism" as it relates to something I call the "responsibility of expectations" that is placed on any game design.