Rashi on Genesis 20:11:1:
רק אין יראת אלהים.
אכסנאי שבא לעיר, על עסקי אכילה ושתיה שואלין אותו או על עסקי אשתו שואלין אותו אשתך היא או אחותך היא:
My (loose) translation:
When a a guest comes to a city, you should ask him regarding (his needs for) food and drink or regarding his wife - if she is your wife or your sister.
How is a lack of asking these questions a demonstration of having no fear of G-d? When a guest (out of town) couple shows up in my shul, on Shabbat, I don't always ask if they have a place to eat (not b/c I'm unfriendly, but mainly b/c it would be strenuous for my wife), and I most certainly don't ask, "Hey, is that your wife or your sister?" So, does that mean that I have no yir'at elokim?
Another question - it seems in his answer to Avimelech, that he was worried that ANYONE might kidnap Sarah, not just the king. Is this correct?