The little marks that use their influence

One of my current pet peeves is misplaced apostrophes -- drives me nuts. It's most upsetting when I see that I've done it myself, but I was born in the '70s for X sake, and I'm allowed to boof it every once in a while. Gimme a break, Nell Carter -- I'll be 38 in a few days. However, when people older and wiser than I repeatedly misuse apostrophes, I want to smack them.
Notes:

1) Apostrophes are not used to pluralize words. It's not DJ's, gym's, the 70's, or Little Shop of Horror's. It's DJs, gyms, the '70s, and Little Shop of Horrors. It should only be used for pluralization on plural nouns: children's books, women's shoes, people's court.

2) Apostrophes show posession: Mother's milk, Jessie's Girl, and The Emperor's New Clothes. In example #1, the misplaced apostrophes imply that someone named Horror owns a Little Shop. THE EXCEPTION: Possessive pronouns. I-T-apostrophe-S does not mean "belonging to it" but rather "it is." Why? Because...

3) Apostrophes are used for contractions and omitted letters. So far I have used I've, I'll, I'm and It's. Don't you, won't you, can't you, aren't you? Shouldn't the gov't care who you'll vote for?

I don't know why this bugs me so much lately, but it does. By contrast, others are bugged by improper use of quotation marks. Sounds like we needed The Electric Company to record a follow-up single...