This is such an annoying thing to me, I think I may have even blogged about it before. I work in a building full of editors. So it's always weird to get an email full of grammatical and spelling mistakes from our receptionist. She suffers from the unneccessary-apostrophe disease that has become incredibly common in the past five years or so. Today she announced that two people were having birthdays over the weekend - except she wrote "birthday's." Why add an apostrophe? Where did this come from? I just want to figure out the chain of faulty reasoning that results in turning plural words into possessives. Is it because "birthday" ends in a "y", and that's kind of a vowel, and sometimes words that end in vowels get a ... No, that doesn't make any sense. Is it because sometimes "birthday" is capitalized, i.e. "Happy Birthday," and therefore it should be treated like the plural of a proper noun, which.... also doesn't get an apostrophe unless it's possessive. Huh. Do you see why this might make an editor crazy??

Listen, I can live with the its/it's problem. (a refresher: you only use "it's" as a contraction for "it is." It's simple. And it rubs the lotion on its skin.) But this crazy, lazy, "instead of thinking, just add an apostrophe" thing is a symptom of the decline of Western civilization.

p.s.
Good: ladies' room
Bad: ladie's room (I really did see this in use)