Okay, at the risk of being a grammar Nazi, please forgive me: It drives me crazy when I see it’s when it should be its and visa-versa. “It’s” = it is. Always. “Its” is the possessive. So it’s its party and it can cry if it wants to, and if its pants are falling down its legs, it’s cool because it’s a tree and shouldn’t be wearing pants in the first place.
So why does it drive me crazy? I make my share of grammar glitches, and having had to speed-read grammar guides when I was 25 and suddenly found myself teaching Basic Comp, it’s not like I know the mechanics of the English language better than many people. It’s just that this little doodad of a grammar deal hits me in a visceral way, makes me roll my eyes at the heavens for no good reason.
There’s even less good reason to be annoyed when you consider how crazily inconsistent the English language is. We could say “Caryn’s obsession with it’s and its is kind of silly,” but if Caryn were an It, it wouldn’t be “It’s obsession” but “Its obsession.” Pronouns get different treatment than regular nouns when it comes to our frenemy, the apostrophe. So it’s logical to say its logical when you mean it’s logical. Sheesh!