Did it ever happen to you that you read someone else's fic search and thought "What an awesome idea, I need to read that!"? And when the fic was found, you went and read it and after a paragraph or two, you had this look on your face - O.o? Where and we're, your and you're are two completely different things! Full-stops were invented for a reason! *shudders* I mean, the plot might be totally awesome but the way it's written is important too!
More times than I can count! Oh, how I long for a red pen sometimes when reading. I'm not sure what's worse: when both story and writing are dire and you can just click away with a shudder, or when there's a really creative story idea buried in there somewhere, begging for release from the tortured spelling and grammar and overwrought depictions!