ec2-34-231-180-210.compute-1.amazonaws.com | ToothyWiki | RecentChanges | Login | Webcomic That factor within science fiction or fantasy which allows you to actually care when the main character is mortally ill rather than pointing to one of the other characters and saying "Um, she healed someone earlier, why doesn't she do that again?"
When done well it is completely unnoticable.
When done badly you'll either end up laughing or crying through the rest of the story (depending mainly on how much you cared about the story before it messed up).
The really nasty thing about SuspensionOfDisbelief though is that it only takes a single flaw to break.
Errors in scientific areas, especially in old sci-fi, are probably the most typical but the worst by far are internal inconsistencies.
My most recent experience though is from a relatively recent (1995) Star Wars novel that SunKitten lent me (and I shall hold you entirely to blame :p ):
... snow frizzing wildly away from a magnetic field... Were it not for the magnetics they would have been buried by drifts in hours.
But it's magnetic snow. One you only get on special planets with metalic water. Which the people happenend to be on... --Angoel
Which novel? --SF, who thought he'd read nearly all of the SW novels and doesn't remember anything as bad as this comment....