It seems like half of the apostrophes I see are used incorrectly. People get confused, I think, because they aren’t able to understand the difference between a plural and a possessive, and they get caught up in a tangle of s‘s and apostrophes. A plural means there’s more than one of something. In that case, you almost never use an apostrophe. The only exceptions, basically, are when you’re dealing with something that’s italicized (such as a book title, magazine title, non-English word, etc.), when you’re dealing with abbreviations that have periods in them, or in a few words or phrases where it’s become standard (“do’s and don’ts,” for example).
Truth be told, I’m not even that strict about apostrophes and plurals. I don’t mind seeing “1990′s” even though some would advise against it. To be honest, I don’t think it looks any worse than “1990s.” And I don’t mind an apostrophe in most abbreviations (VIP’s or TD’s or whatever). So I’m pretty damn lenient about this issue. But when I see people taking run of the mill words and sticking completely unnecessary apostrophes into their plural forms, I feel like vomiting. On the plus side, I also get to feel superior to all the idiots in the world who don’t know the rules of English grammar, but the nausea is a problem. Sometimes people stick apostrophes into words that aren’t even plural. For examples, see Apostrophe Abuse.
P.S. As always, my resource for the English language is the second edition of the Writing Handbook by Bernard Streicher, S.J., a revision of an earlier work by his fellow Jesuits, Kammer and Mulligan. It is undoubtedly the finest contribution the Jesuits have made to modern American society.
I share your urge to vomit when faced with misused apostrophes. I hadn’t come across the Apostrophe Abuse site– love it. Why the hell didn’t I think of starting a site like that?